I came around the corner last Saturday and had one of these right in my face. It was hidden and I was flying (new trail, never ridden) and juuuuust about took a header. Saved it, barely. It was funny, because there is a simple line just to the right. I saw it on the second go-round. Lordy, what a sport.
Sounds like you just about heard some serious chin music ringing in your ears. Those close calls remind me of times before clip-ins where feet would come off and the only thing stopping a hard end-o is luck and the fact that the ischeal tuberousity landed directly on the wavering seatpost!! Good golly... so close to disaster and a good dentist appointment.