I crashed earlier this spring (rr tracks with the wooden ties, tried to avoid a splintered section, zigged/zagged maybe too abruptly and tire must have slipped on the metal rail). I have spd clips. When my friend came back to pick me and my bike out of the road, she asked me how I got unclipped. I don't recall unclipping but must have unclipped in relation to the fall. I was upright, then laying on the ground in less than a blink of the eye. Unclipping was my last thought, and I think it was done by mechanism alone. Glad you are okay, sounds like quite the tumble you took..