Well not actually a "loss" but in my previous class, a year ago, I've lost one of my USB-Sticks.
And suddenly, a year later, some random teacher got into class and asked for my name, then gave me my USB-Stick back! After one year!
I didn't remember the stick in the first place but then I realized it was the one I've lost!

Btw it was a 2GB one, with just a few files on it...