Never happened to me yet, probably because i'm one of the very few that live car free here & where i go & leave it locked up, bikes are a rare sight aside from teens on their ill-fitting bmx's.

As far as locking up & stranding.... Duct taping the lock's key on the top tube is always an option? I try to carry duct tape with me wherever i go. I have a victorinox rescue tool, but to free my bike i'd need at the very least a multi-tool.

Around here, a simple call to FD would have them come cut the lock off most likely, but in some areas i can definitely see that not being likely.

- Andy