Sounds like someone might have put the front wheel in the back of a car, and left the back one on the ground, and maybe hit a bump cause the bumper to hit the gear selector and popped it in gear.
Otherwise I don't see this happening any other way, it just doesn't pop into gear, unless something else caused it.
Also no other posts from the OP since his first.
I say start it, if there was any damage, it's already done.