I'm so sorry to hear that! Who would have thought they could get stuck like that!
I lost a bantam cochin pullet last year when she jumped up on a bale of shavings and fell head first between the bale and the wall. The space was so small she must have wiggled until she jammed herself tight and couldn't breathe. Feeling sad for everyone who has been losing their animals. I felt bad, too, but there is no way to anticipate everything that can happen.