They are something given their size. I had the same thing happen a few years ago in my garage, saw some movement along the shelving in the opposite bay one morning. The garage door gasket and sweep on the jamb, on the bottom corner had been chewed out by a chipmunk that got in when the door was opened, then closed, so there was a way in and out.
As a hobby, I've kept a cage with a small clan of voles, I use the manure or old bedding to make compost on a small scale. I actually collect the sawdust and chips from cutting wood, dry it down for bedding. I collect grasses dried down just like hay, nice green hay on a small scale, they really like it, nice healthy friendly little guys too, I've had 5 or six for years now, and its helped me build up great soil in my small garden patch near the house. In every group of these, there's always one that is very friendly, so there will be a favorite one in the bunch. A few years back I had one that I caught as a juvenile, she was something else, just tap on the nest, she comes out every time, jumps into your hand, I never bribed them with food, they just like the attention it seems. She was getting old and you could see it, getting feeble and wobbly as she walked, just like us, though in the wild, they never die of old age being the meat supply for so many predators.
So the weasel, in his winter attire finds his way in, and somehow gets past the snug hardware cloth lid on the cage, a glass aquarium, and I notice there are voles missing and of course he's taken the old feeble one.
Sure enough as I am quietly standing there, this weasel shows right up and is ducking in and out of places, he wants to get at that cage, but I'm in his way. I could not believe how brazen he was. He ain't gonna out smart me though LOL, so I take a tool bag with a zipper and place it near me, within reach, and I wait, sure enough he eventually goes right in the bag and I zip it up, caught him, well not yet, now I have gloves on and have to pin him so I can grab him and that went fine, he was nothing once I caught him, p*ssed off though. I put him into a galvanized steel garbage can and put a lid on it. I took photos and a video of him. In one part of the video, I got him to strike. You cannot believe how fast he was, what a fierce little tasmanian devil! Later I took him down to the edge of a large pond at the bottom of the hill, let him jump out into the powdery snow and he scampered back and forth looking back at me, then disappeared.
At some point later, maybe later that year I had a female vole and some young, something you have to do every so often as they only live 2 years, though I have one right now that is older than that and very healthy. She is the sister of the one with the young. So I had them in a bucket separated from the cage til the young open their eyes. I look in one morning and the mother was dead, 2 distinct puncture wounds on her head, the darned weasel came back, but could not carry the carcass out of the bucket. She was the most docile, lay flat in your hand and loved attention, so after some years I seemed to have domesticated these, selected her for the next brood. The young survived as they had opened their eyes and were agile enough to escape, that weasel would have taken any of those or at least killed them. I still have them today, they are 1 1/2 years old, the 3 of them.
I repaired that garage door gasket, and I've never seen another weasel. I am sure he was attracted by scent, though the cage is cleaned 2x daily and or sanitized regularly, he certainly knew where to find prey.
I've got a new mouse trap too. I placed some snap traps on the trim over my front door, darned deer mice climb the brick and had used a small hole to get into the soffit/overhang. So I see a trap went off, older trap, spring not as strong it seems, little hantavirus carrier is still alive, so I said what the heck, I'll give him a reprieve, put him in a steel garbage can, take him far enough across the field, he'll either make it or be prey. I check in on him the next morning, there is another one in there and they know each other, if they don't they tend to fight. Somehow he got in, and there has been none in the basement, traps been clean for a year. I figure he climbed the wheel of a cart near the can, dropped in, could not get back out. Their sense of smell is beyond comprehension, so it works out, had no idea one was in the garage, did a good deed with the stay of execution and I got rid of one I never knew I had ! LOL !