On one particular camping trip I had the van all loaded up and still had a bag of garbage to dispose of.  Reluctant to put it in the car, I placed it on the roof of the van with the idea of putting it in the dumpster on the way out of camp.  Well at least that was the idea.  When I got home I realized I never actually did this and it was no longer on the roof.  So somewhere in the 150 miles between the camp and my house it fell off, oops.