Ouch. Todd's right though. A ratchet would have done the job sufficiently.
We all live and learn though. If that happened to me, I would take the rest of the UIM off the car (if it isn't already) and try to clamp something to the broken bolt, something with teeth and can be made pretty tight..
My brain's not working. I know there has to be a tool you can use that will twist it loose.. good luck with it!
