I loose things all the time, but somehow they always get back to me. The worse was when I left my graphing calculator (this big, expensive kind required for calculus classes and such, not something you can easily replace!) at a gymnastics meet. I took it there all the time b/c I had made a spreadsheet for scores and would enter them in right away. I left it at the City Meet, so our season there was done. I thought it was gone forever when two weeks later, a coach brought it over to our team. Phew!
I've also lost my college ID card a lot. It's pretty bad b/c it's what we use for all of our meals so if we don't have a card, we don't eat. It's even worse for me b/c I work on campus and have card-access to all of the buildings almost 24/7 so not having the card makes it hard to get around. If you loose it, it's $20 to replace. One time I lost mine for days and finally the Bookstore woke me up one morning to say they had it.
And one more good one.....I used to deliver papers as a side job and the Sunday paper is due by 8am. In Michigan when it snows, you have to be out there before 7 to get it done in time (our press weights 5lbs each on Sunday). One morning I was trudging along and found $40 right in the middle of the street. The next day my friend came over and she always steals from people so I quick hid the money inside of a book. Later, I looked EVERYWHERE for it and couldn't find it. Last year, I was looking through that book and found a copy of TIME with Bono on the cover inside and inside the magazine I found the $40.