happened to me, I put a volitan in my tank (with 2 damels and a clown) one of the damsels got eatin, he was the "dominant" one so he obv tried to challenge the bigger fish, the other i thought got eatin but was hiding in a rock for over 3 weeks, I was amazed at that. I fed him and saw himj eat after that, but either the volitan or the grouper got him, or he jus perished in the rocks hiding. moral of the story, they can and will hide in the rocks for longer than you think its possible