i had a fish get stuck in a rock and die like that too! my wifes purple psuedochromis "Glowna"...
i was doing some tank maintainance and i had taken all the rocks out of the tank, but while i was removing the rock the fish swam into a hole in one of the rocks. when i was done i put everything back in the tank expecting the fish to come back out when things settled down. not the case at all. a few hours later i saw a bunch of hermit crabs huddled around the same place on a rock, and apon further inspection i noticed the fishs head poking out of a hole, and the crabs had been eating the face! i couldnt believe that a fish could have possibly gotten itself into a situation like that? i thought they were a little more crafty than that! :lol: