Boy I hate when this happens. (and it happens all too often to every one of us). I was changing the scope on one of my varmint rifles when I dropped one of the scope ring screws out in the garage. I heard the screw land right next to my feet, but that didn't matter because it has passed into another dimension and vanished from the face of the Earth! I was down on my hands and knees with a flashlight looking for it for half an hour to no avail. Then I swept up everything in a 6 foot radius - again, nothing!
This has happened so many times over the years with tiny parts, small screws, that one of a kind tiny tool that you just finished making, and worst of all that tiny spring loaded steel ball under the extractor plate on a Savage bolt head that flies off into oblivion, that I know for a fact that when you drop something it opens up a porthole to an alternate reality and vanishes forever. Actually that's not true - it is possible to find that part again: All you have to do is buy another one, and five minutes after you get the replacement the old part will appear again by magic.
The probability that you'll drop and loose a part increases exponentially depending on the situation. If it's some zillion dollar gold plated piece of hardware that you've waited 2 years for it to come back into stock - Oh, it's just gone! If it's a part that only costs 2 cents, but you can't finish the build without it, ditto. But if it's a common hardware store part and you've got a hundred more in a box in some drawer, I'm just surprised that it doesn't jump right back into your hand! But I wouldn't be surprised to find out that somewhere way out in deep space there's some lonely world that has a ring orbiting around it made up of all the tiny junk that we've dropped and never been able to find again.