So, um, there are a number of references in this one to several of my sister's headcanons/other stories. If you wanna read 'em, she's Exactlywhat on archiveofourown.org !

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It started with Prowl's datapad. His favorite one, the one he wrote the daily duty roster on. And his personal, private diary. It was missing. When he consulted Ratchet (he had been in the Med Bay earlier that afternoon), he found that Ratchet was missing one of his favorite throwing wrenches, the one the Twins had modified into a boomerang. When he approached Sideswipe and Sunstreaker (the usual culprits of missing objects), the Twins were in a frantic search of their own. The yellow Twin was missing a painting set.

The first monster Prowl happened upon was looking for things of her own as well. The monster Royal Scientist was wandering down the hall, looking into every nook and cranny.

"Ma'am, I hate to bother you-"

Alphys turned around with a surprised squesk. "Oh! O-oh-- it's just you, P-Prowl. I-It, is, uh, Prowl, r-right?"

"Indeed, Ma'am. Is there any way I can help you?"

The small saurian monster fidgeted, nervous. "U-um... I- I mean, if you could-... Um... No, i-it's fine, I'm sure y-you're busy...

"Not particularly. I am just searching for a datapad I seem to have... misplaced."

"Oh! M-maybe we c-could help each other, t-then! I, uh, l-lost my glasses." Alphys shuffled her feet a little, self consciously adjusting the glasses perched on her face. "I mean, I h-have these! A-and they are g-glasses! B-but I lost my good pair, a-and these ones are all scratched up, a-and i-it's kinda hard to see-..." She trailed off, realizing she was rambling.

Prowl hummed thoughtfully. "Of course. I'll add your glasses to the list." The Second in Command of the Autobot army nodded politely, and strode away.

"L-list?" Alphys stuttered as she watched the mech walk away.

~o0o~

Toriel was looking for her snail book. It was her favorite book, with over forty facts and uses about and for snails. She had been planning to make a snail pie for dinner that evening, but could not quite remember whether three or four cups of snails were necessary. The only place she had taken the snail book recently was the Arc, so, logically, that was the place to look.

As she wandered down the halls, retracing the previous day's steps, she came across Sans. After a brief pun-filled greeting, he expressed that he was searching for a sock, and she promised to keep an eye out for it. Not long after, she passed Frisk, who had misplaced the locket they usually wore snug around their neck. Toriel promised to search for it, too.

Prowl found Toriel in the commissary, where they had shared a meal (energon for him and tea for her) the day before. She was under a table, and he only managed to not squish her as he made to sit down with his afternoon energon because of the alert in the back of his HUD to check for humans (and, more recently, monsters).

So, chair pulled out, half sitting, Prowl greeted her. "Queen Toriel, a pleasure to see you. Might I inquire as to why you are under the table?"

"Oh, it is nothing." She smiled up at him, stepping back from the table. "I am simply retracing where I was yesterday. I seem to have lost a favorite book of mine, but I recall having it in the Arc."

"Ah. Yes, I do recall you having a book yesterday. I myself am looking for a datapad."

"Oh, really?" Toriel let out a bemused chuckle. "I suppose I will add that to the list, then!"

Prowl paused in sitting down. "You have a list as well?"

"Yes. Sans was missing a sock- which is, frankly, not a surprise- and Frisk, their locket. You have a list?"

"Yes. My datapad, obviously. Ratchet's boomerang wrench, Sunstreaker's painting kit, and Jazz's... Well, honestly, I'm not sure what he lost. I only know he's looking everywhere for it and he said he, quote, 'really really really really really hopes someone with evil intentions is not the one who
finds it."

Right about then, Sunstreaker wandered into the commissary, Papyrus riding on his shoulder. Papyrus appeared to be explaining to Sunstreaker the nuances of fine puzzle building, but paused to give Toriel and Prowl a happy greeting.

"Did you have any luck in finding your painting kit, Sunstreaker?" Prowl asked, no greeting. He and Sunstreaker shared some common beliefs, one of which was that trivial talk was, well, trivial.

"No. It's gotta be somewhere, though. That was my good kit. Never took it out of my room. I'll find it soon, I'm sure. Sideswipe is just a mess."

Papyrus frowned rather suddenly. "You're missing something, too? I bet I knew who took it! It had to have been that thieving canine!"

Prowl and Sunstreaker glanced at each other. "Thieving canine?" the yellow Twin queried to the monster on his shoulder.

"Yes!" Papyrus gestured, suddenly becoming quite agitated. "That Annoying Dog steals everything! I still haven't gotten my special attack back yet! If you're missing something, that dog probably took it!" Then his expression turned to something a little more thoughtful. "It has this... way of getting anywhere you don't want it to be... Kind of like my brother..."

Prowl allowed this new information to turn over in his processor for a moment. "Hm. If this... canine... is running around stealing things... perhaps I must notify Optimus and compose a base-wide alert. Is there any more information I should include in this alert? A description of the perpetrator, perhaps, or common themes in things he takes?"

"Well..." Papyrus rubbed his jaw with a gloved hand. "It's small. And white. And it steals things!" He grinned, seeming to think this was a good enough explanation. On everyone's waiting stares, he continued. "... I never actually get much of a good look at it, because I always try to chase it away before it can steal more of my attacks. But Sans and it are good friends! They avoid work together all the time! You should ask him."

Prowl nodded. "If you can send Sans to my office, please, I would like to talk to him after I speak with Optimus. Thank you. I must go, I have things I must attend to." Like rewriting the duty roster that had been on his missing datapad.

... at least if it was a dog, it wasn't reading his diary.

Optimus wasn't in his office. He wasn't in the Med Bay. He wasn't in the Command Room or the Planning Room or anywhere else he frequented. And he wasn't answering his comms, which, Prowl determined, probably wasn't good. So Prowl went to the one place his tactical computer figured would be the most likely place Optimus Prime would be; his quarters.

Upon knocking on the door, Prowl heard a loud crash, a solid bang, and a low, muttered "frag!"

"Prowl here, Prime," the tactician stated, pressing the intercom button on the door panel. "I have something to inform you of before I make a basewide alert."

The door whooshed open to reveal a haggard looking Optimus Prime standing amid the ruins and wreckage of what once had been neat and orderly quarters. Prowl looked past the Prime, stunned to the point of staring.

"It's gone, Prowl."

The black and white blinked. "What is gone, sir?"

"The Matrix. The Matrix is gone. I can't find it anywhere. It's not... I looked... HOW DOES A PRIME LOSE THE MATRIX? IT'S STUCK IN MY FRAGGING SPARK CHAMBER!"

Prowl was still for a moment as his processor took in this new data. "Annoying Dog," he said after a half-second, turned on his heel, and marched away toward the Officers' offices.

Optimus Prime stood in his doorway watching the bobbing doorwings of his Second in Command rush down the hall. "... 'Annoying dog'?"

Papyrus, meanwhile, was beginning to think that, perhaps, the Annoying Dog had not only stolen an assortment of items, but his older brother as well. He had searched high and low across the Arc with the intent of delivering Prowl's summons, but had yet to find his brother. As of that very instant, he wasn't too concerned, as Sans did have the habit of being nowhere you wanted him to be, but it was still somewhat frustrating.

Coming around a corner in the hallway, Papyrus paused when he saw Prowl coming from the opposite direction. "Oh! Prowl! I haven't found Sans yet, but I'll be sure to tell him to find you when I find him!"

Prowl nodded. "I appreciate it, Papyrus. Please ask him to hurry. Optimus Prime has come up with a very important item missing and I believe the Annoying Dog might have had something to do with it. Thank you."

And with that, Prowl keyed open his office door.

... Only to find a short skeleton dressed in gym shorts, fluffy pink slippers, and a blue hoodie sound asleep in his desk chair.

"Well. Our immediate problem has been solved," Prowl threw over his shoulder to the skeleton still standing outside. "I've found your brother."

Papyrus stepped into the room, frowning as he saw Sans. "Sans!" he shouted, waking said skeleton. "What have I told you about sleeping in places that aren't your bed?"

Sans blinked, sitting up slowly. "uhhh..." he mumbled, still waking up. "... don't do it?"

"Yes! And what are you doing right now?"

"...well... i'm not sleepin' any more."

Prowl (himself a fan of sleeping in places not beds) waved Papyrus away. "Papyrus, I am more happy right now that we've found Sans than I am angry about him sleeping in my chair. Sans, for the record, I have no problem with you sleeping in one of my chairs, or anywhere else in my office, as long as it is quiet and not hindering my work. But we have other business to attend to. Sans, do you know the location of the Annoying Dog?"

More than content to have been given the go-ahead to nap in a quiet place, Sans had already flopped back down. "ehhhhh... he's tricky to pin down. why? did he get somethin'?"

"A lot of somethings. From a lot of people. Some of which are very important. I and others would be very appreciative if you assisted us in finding the Annoying Dog and in re-acquiring our items."

Sans let out a sigh as he pulled himself up again. then he proceeded to climb off Prowl's chair. "welp. alright, then. guess we'd better start searching." With that, he promptly meandered out the door.

Prowl stepped out after him. "Where are you going to look, and what can I do to help?"

"weeeeelll..." Sans said slowly, "i know he likes to share some of my good napping spots. anywhere hidden. like those storage rooms. or the chemical processing room. oooohhh or the arc's cockpit. there are some really comfy chairs there. i fell asleep in one of those once, and it was one of the best naps-"

"SANS!" Papyrus interjected. "Stay on topic!"

Sans let out a dejected sigh, but continued, listing off a variety of out-of-the way places.

"So," Prowl began, trying his best to make sense of what Sans was saying (experience with Bluestreak helped), "You are going to check the storage rooms, while I check the chemical processing rooms and whoever finishes first checks the cockpit, and then we move on to the rest?"

Sans shrugged. "sure." Then he turned to Papyrus. "whaddabout you, bro?"

Papyrus put his hands on his hips and gave Sans an expression that said it should have been obvious. "I'm coming with you to make sure you don't slack off more!"

Prowl nodded. "Okay. Search begins now. I will send out a basewide comm alert now and ask other mechs to begin searching, too."

~o0o~

::ATTENTION, AUTOBOTS! This is a basewide alert from Prowl. Items have been coming up missing and we are almost certain we know who is the culprit. It is a small canine creature which followed the monsters here. It has been likewise stealing their items, as well. A basewide search is being initiated. Feel free to join in at will. Search everywhere and anywhere. Intelligence suggests it will not be far away, likely on the ship or nearby. If found, please alert myself, Jazz, or Optimus Prime immediately.::

~o0o~

Sans and Papyrus wandered through the cockpit (after meticulously searching through storage rooms, with the help of Autobots called into action by Prowl's comm), searching for the Annoying Dog. Well, Papyrus was searching. Sans was continually settling down in chairs or atop computer banks, only to be motivated back into action by a shout from Papyrus, only for the process to repeat itself. Yet, despite the tall skeleton's persistent hunt and short skeleton's considerably less persistent hunt, the dog remained unfound.

~o0o~

The chemical processing room turned up no canines of any sort, just a few stray rodents of earthen nature and a number of quietly humming machines that operated for the most part on AI. Prowl left the room, pinging Teletran-1 with his location and the status "Cleared, no dog" on the map the other Autobots had started to organize a search. Room after room changed from darkened blue to tinted red with the small glyphs attached as mechs cleared them.

With a soft ex-vent, Prowl left the room and headed toward the fuel containment area.

~o0o~

Alphys and Undyne had teamed up to search together. They were currently searching through a long-since caved in hallway of the Arc, one that had been smashed into the side of the mountain. Unfortunately, the room was proving to be quite Annoying Dog-free.

Undyne sighed, patting Alphys's shoulder. "Don't worry. We'll find that dog. And when we do-..." Undyne cracked her knuckles, letting the threat hang in the air.

"Not if I get him first!" a voice hissed from a side hallway they hadn't gone down yet. "He took my crystal spark sculpture! I got that on the orn I turned a thousand vorns old. I've managed to hold onto it this long – I'm not letting some annoying cotton ball with legs take it!" Mirage ranted as he shimmered into visibility.

"Yeah?" Undyne countered. "Well at least you can see without that! Alphys's glasses were taken!"

Alphys quietly reached over to grab Undyne's hand. "U-Undyne. It's okay. I h-have my spare pair."

Mirage sniffed. "Perhaps I can. But it is the sole remaining item I have that was given to me by my creators. The Towers I lived in are but rubble on a planet orbiting a dying star. My people are all dead, and that crystal is all I have left of them besides memories." The rant was quiet, but heartfelt, and the blue and white mech didn't look at the monsters as he spoke. "It... is one of the few things that is important to me. In either case, though, we are all looking for the lost items. I see no reason for us to argue. If I remember correctly, this particular hallway is caved in a short distance down. If you have already searched it, I will mark it as cleared on Teletran-1's map."

Undyne just nodded, and the mech and monsters' search was quickly recommenced.

~o0o~

It was Steeljaw who found the Annoying Dog. After literal days of searching, metaphorically turning the Arc on end, and every Autobot and monster being recruited to the task, the thief had been found.

Everything had been searched three times over, and most had pretty much given up on finding the fluffy creature. The fact that so much was missing (the Matrix, particularly) was taken in stride by the Autobots. Everything else had pretty much been lost, so why not this, too, just because fate liked to say frag you to them.

Steeljaw had been taking a shortcut through the air vents from the commissary to Blaster's and his cassettes' quarters when he heard quiet, echoey yipping. Curious, and also still on the Annoying Dog alert, he followed it, examining the map of the Arc as he padded silently through the narrow tunnels.

And as he came upon the slats of the vent and the source of the shrill barking, as he compared where he was on the map, he realized why no one had found the dog.

::Prime, Prowl,:: he commed immediately, ::I've found the Annoying Dog.:: With the comm, he sent a live-stream video of what he was seeing; a small, fluffy, canine creature surrounded by stuff barking conversationally at a glowing orb of sparkling energy.

::The air filtration unit. We searched the mechanical systems room it's in, but we never searched the actual unit itself. ... Primus knows how the glitched thing got in there,:: Prowl commed back. ::Steeljaw, good work.::

~o0o~

It took some figuring, but Wheeljack managed to get the inner workings and the interior chamber of the sealed air filtration unit open. When he did, he was greeted with the sight of a mass accumulation of strange items, but no Annoying Dog. Everyone got their things back.

And at the bottom of Prowl's most recent diary entry was one word that he hadn't put there.

"Bork!"