A few years ago, my keys accidentally dropped down the elevator shaft of my building. (There's a narrow space between the elevator car and the wall, big enough for a set of keys.) The building manager told me there is no way of getting them back.
I bought a new set, pretty expensive, as my car remote was on it. About 6 weeks later, a clerk from the manager's office came running down the hall, calling me. She had my keys! Turned out some maintenance workers had been down there and turned my keys in to the office, and she remembered that I had reported mine down there.
It was nice getting them back, but would have been even nicer before I spent a fortune on the new car remote!