I found him! He went inside the cave of the decor where I always wanted him to go in the first place! Goodie! I have put in some frozen bloodworms inside it for him to eat and not have them stolen by my piggie fish that seem to get all the food. My other fish are too big to get inside the cave so he has some peace and quiet to enjoy his bloodworms. That was the last place that I looked because I wanted him to go in, it is usually the other way around as fish don't do what you want them to do or go where you want them to go. This Gobi realized that he needed a good hidey hole and I hope that he uses it all the time so I can feed him in there. If I put bloodworms in it all the time, I am sure he will know that is his dining and sleep area.