When I was studying animation at a private 
University in Los Angeles, one of my friends 
borrowed a bike from the school chapel's Priest 
just to ride up to the Safeway on the corner.  He 
didn't chain it up, and was gone maybe 5 minutes, 
and came out of the store just in time to see a 
homeless man jump on the bike and start pedaling 
furiously away ( apparently, he had never owned a 
bike before, because he could barely ride in a 
straight line ).  The homeless guy rode out into 
traffic, was nearly hit by serveral cars, and 
dropped his old dirty bag of belongings as he was 
trying to evade my friend who was trying to chase 
him on foot.

Needless to say, my friend had an interesting 
excuse for the Priest as to why he couldn't 
return the bike...

Sorry it had to happen to you, tho!