This is pretty much in line with my experience. Once it was completely dark I didn’t have any trouble seeing him. He did pull his head back in when the red light was directly on him but other that that he wasn’t that shy about sticking his head out from a few different holes in his ‘home rock’. I really wanted to be sure I was pulling out the right rock. Even though I was 99% sure I still started to have doubts when hanging that rock out of water but above some salt water for 24 hours did nothing.If it’s a bobbit I’m surprised it didn’t finish off anything fleshy overnight. The one I encountered completely ate 2 scolys, 3rhizos, and a clam. I finally saw part of the head using a red flashlight, it was quick back into the rock. It knew I was there, either senses the light or some one trying to see it. The only way I got rid it was to remove the Tonga rock, it was purchased live rock, broke it open to see the monster and it’s many tunnels. bugger was long, very ugly.
could you clear away sand to expose the tank bottom at a particular area and leave something there to entice him? Would mean he would have to expose himself. The fact that you haven’t seen him is giving me doubts.