Some years ago, a Virginia State Policeman was gassing up his patrol vehicle at a gas station in, I believe, the Manassas area. His duty belt had gotten bollixed up, and he decided to adjust his gear. He drew his service pistol and set it on the roof of the Crown Victoria, while he addressed whatever was bothering him. You guessed it. The pistol (IIRC, it was a Sig 226) went bouncing down the road. It was retrieved by a solid citizen, and he got it back, but ouch!
I once had a S&W 642 fall out of an IWB holster when the whole rig, belt and all, just flopped over. Bad juju, but I was in a single-stall head, and I had the whole place to myself. Yikes. That led to some adjustments in approaching public restrooms. Don't want the revolver bouncing under the stall. "Daddy, look, a gun!"