I buckled my surfboard, but continued to ride for a while. It was bent and flexing just in front of my rear deck-pad.

I couldn't turn without crashing, but all of the sudden I was blasting upwind at a ridiculous angle.

Was this just some weird coincidence or is there something going on there?

I assume your rear foot was put just after the "buckle", or ?

At least, if this is the case - you have put a much flatter tailrocker (or none or negative) into the tail, so it will (might) shoot upwind

A very special experience, and to some point a coincidence, but pretty likely it could happen

Peter