I had a typical disappearing dropped part episode. I was fastenening a seat onto the rails, and the bolt, nut, and one of the plates dropped onto the floor. I found everything but the bolt. After 40 minutes, I still couldn't find it. It was a big bolt, and there wasn't much stuff on the floor.
I thought I was losing my mind, and I checked to see if it had fallen into one of my pockets, or perhaps I didn't have the bolt to start with.
Finally, I looked at the rear brake and there it was.