Slope all your gravel so it's high in the back, and low in the front. Position your decorations so behind them is only gravel and then your fish will hide in front of them. This works great with slate.
That's my question. Wanna make sure this little guy is healthy and that he's just being typical for his species.
But, I do have to say that I have a Spotted Raphael that I never, ever see. Well, that's not totally true. I get to see him when I completely dismantle the tank and pull his piece of wood out with him stuck in it. Went so far as to him making both moves over the years in the bucket of driftwood. Some cats are just completely recluses.