I don't know anything about this topic. It occurs to me that trapped by abalone could be a more sensational way of explaining various accidental means of death while hunting for abalone. Even today abalone pickers regularly die. I know this is not what hikermor is asking...

Found this on https://www.scubaboard.com/community/threads/can-someone-get-stuck-in-a-giant-sea-clam.519725/

Quote:
I've pulled abs before with no iron by sneaking up on them and getting a few fingers under the mouth when they are foraging and quickly yanking them off the rock before they have a chance to do anything.
I've heard though that even if they do clamp down you can pull hard and actually pull the shell off the meat if you have to.
Big rock scallops scare me more than abs. I've had then snap down hard and fast causing some serious pain on my fingers.