Wow. I had no idea that was something that could happen. I would have expected you to wake up before damaging yourself like that - sort of like falling asleep in the bath tub.
I've heard it called Drunk's Palsy (long term effects) or Saturday Night Palsy (shorter term, less severe). Falling asleep in such a way that circulation is cut off to an area, causing damage that normally your body would move to prevent. Drugs and alcohol impede that input to the brain so you don't toss and turn as much, I guess.
One day last year I noticed I couldn't feel part of my leg after my wife had sat in my lap for a few minutes earlier in the night. It freaked me out as I still had no feeling in it the next day. The doctor told me it was pinched and would regrow over time. It took about a month to get full feeling back.
The phenomenon is well known to bondage affectionados who know what they’re doing. They will regularly get pinched nerves and lose sensation, which is an absolute no-go to just «power through». Communication is essential, and many learn to subtly shift to stop the pinching without completely stopping the scene.
Accidents are really frightening, and can happen due to inexperience, carelessness, lack of communication or just really getting caught up in the monent.