I lost a celtic coin from about 200 b.c. off of my desk. it as there and then it was gone. I have never found it again.
I guess I am more organized than I realized. Don't have a problem losing coins, most of the good stuff is in the bank safe deposit box. My problem usually surrounds "I can't believe I just did that" when cleaning a coin or otherwise trying to improve it. Also a few rim bumps I have added over the years dropping coins. That almost causes physical pain when I do that(!)
I once dropped a $1 Sac in the heating vent when I was about 4....Nothing too majjor but still kinda sad. On the other hand, my Aunt's dad recently passed away and they were cleaning out the house. They knew that he had a large popcorn tin container FULL of Mercury dimes, but they can not find it anywhere...