I have one. It was in the tank when I bought it. They said they hadn't seen it in a couple mo. before I got it though. It does usually stay in the rocks but it has a certain cave it loves to hang out in so we can usually at least see him in there. But low and behold this morning when I fed them, he came right out in front and ate more than I have ever seen him eat, guess he was hungry!! Usually he hangs back and just eats what ever happens by (I feed them frozen brine shrimp)
When he is out though it is worth the wait, he really is a cool fish. He does seem to come out more when the lights are off though.