Sounds like a tough ride. I haven't had a clip in failure in a while, but the memories are still fresh. Maybe 20 years. I was mountain biking with an early pair of spds, got some mud in them and they wouldn't release when I got to a gnarly spot. Ended up tipping to the downhill side, head down the hill. Had to take the shoes off o extract myself. Could have been worse.
I have failure-to-unclip failure regularly (and wish I had thought to buy my mirrors in bulk). The best was with a loaded touring bike in a scenic pullout on the Blue Ridge Parkway, filled with elderly leaf peepers. My bike had my lower leg pinned down so I had to flop around for a while to figure out how to free myself. Some nice man grabbed my arm to try to help me up but I was so slimy with sweat he couldn't get a grip. A humbling memory to help me get over my pride...
It wasn't a failure to unclip, but two years ago when I crashed and broke my wrist, I needed help to get the bike off me so I could get up. Couldn't figure out why I couldn't get up until I saw the funny angle my hand was pointing.