While travelling I once stopped for gas, and I must not of tightened my gas cap properly. A bit later I overflew an airfield with a VOR, and as a passed the VOR, I turned to a new course. As I turned, I caught a glimpse of movement out of the corner of my eye, and immediately noticed it was my gas cap, as one of my gas caps was now missing. I entered the pattern of the field I was overflying to land to see if I could scrounge up a gas cap. As I touched down on the runway, a small red object on the runway caught my eye as I went past: IT WAS MY GAS CAP! I taxied back, picked it up, and screwed it back on. Still working today (with the addition of a few dings/scratches from its fall from 3000 feet).
I have to admit, my luck doesn't normally run that good.