Set a screwdriver on the fan shroud of a car I was working on, and it vanished. I knew it was there, but darned if I could find it... until we were test driving the car, and WHANG Winka winak Brrrrrrrrrrrr... It had fallen to the bottom of the shroud, and during the test, had ended up getting picked up by the fan and flung into said shroud. About 1/4" forward and I would have bought a new radiator.
I was working on a 1923 Model T, I had several tools out. When I finished, I moved the tools that were under the car to the center of the floor, under the car. When I moved the car out of the shop, leaving the tools centered on the floor. It's easier to pick them up when the car is gone.
Not a tool... I was tightening bands on the '15, and went to button it up... and was missing a nut. Anyone who has worked on these knows that anything can (and will) fall in that big inspection cover hole on the hogshead (the cover over the transmission and flywheel), and fall to the bottom of the engine pan under the flywheel. That little wrench that came with the car is usually the culprit, but the nuts off the end of the shaft can do the same thing. If you DON'T get it, whatever will then find its way to the magnets on the flywheel, thence to chew up your magneto coils, which makes that a real expensive and time consuming mess.
So here I am fishing around with a magnet feeler in the bottom of this flywheel case, where you can't see, and thereabouts a gallon of dirty oil lives... and nothing. So realizing It's gotta be in the flywheel, I pull the hogshead off (a whole new not a fun job either), and check... Nope, not in the magnets, not in the bottom of the pan, not in the transmission, not between the bands and drums... and now I'm getting pissed and frustrated, and I look over at the seat, where I put it so it wouldn't fall into the transmission...
So I get the whole cursed thing back together, an snugging the last band, and the little wrench slips out of my hand. Actually, I think it was Henry's ghost that slapped it out of my hands, into the depths of oily hell...
All over a stupid nut. Nuts is just about right!!!