Well, there was this one time
that I put the kid's babyseat on the roof.
Just kidding.
26 years ago I put my wallet and some keys on the roof of my car and drove away. I didn't need my keys for that car, the lock was broken on the steering column. And I might have used a screw driver (or wire coat hanger) to get into it. But it was my car, really. So I didn't pay attention to keys while in it. I saw/felt them bounce behind me.
That screw driver was good for getting into that apartment as well. Can you tell I've lost a lot of keys?
That was the last time I recall it happening to me.