Haven’t encountered blank bodies myself, but from what I hear, they’re not incredibly threatening. They can deal damage however, so it’s possible that it was hitting you while you were asleep, and you woke up with no HP left. I don’t really know how that works, because I usually wake up once things are near me. If you have Heavy Sleeper, though, it’s possible that that is the case.
Or… you might have overdosed on drugs. I’m pretty sure there’s an invisible value that determines how many drugs you can consume, and if that goes to far in one direction you just straight up flop over dead.
Other’n that, iunno.