When you say 'without permission' I'm assuming that the YO wasn't requested to work the colt, in which case, how odd that the YO would take that upon herself.
I'm guessing she means he became entangled in the fencing around the arena? Sounds like an accident to me - the horse could easily have become entangled in fencing with or without a bit in it's mouth, and with or without being in an arena.
I felt sick when I had read this thread. What right does anyone have to mess around with a horse that is not their own without permission. It's bad enough if it is an older horse - but a youngster - god only knows what that YO was thinking. There is one thing for sure - I would be down on that YO like a ton of effing bricks making sure EVERYONE in the vicinity knew that YO was not to be trusted. Would also make damn sure I got compensated - not because the money would matter - but because that YO deserves whatever they get.