He's likely buried in the sand -- this is how they sleep, and also a defense mechanism. If they're frightened, leopards will dive into the substrate and only come out when the coast is clear. Sometimes they hide for days when they're newly introduced. Whatever you do, don't go digging -- let him come out on his own.
Leopard wrasses are notoriously difficult fish, mostly because they don't ship well and tend to arrive in pretty bad shape. Many refuse to eat, and some can't because their jaws are damaged from trying to bury themselves in the bag during shipping. If your wrasse is healthy, he may only eat pods from the rockwork at first. They're 'pickers' (in nature they eat things like forams and pods), and sometimes have a tough time learning that the stuff falling from the sky and floating in the water is food. My Potter's (AKA shortnose leopard wrasse) took a while to adjust; at first she just picked bits of food from the rocks and sand. I had to overfeed to make sure the other fish would miss enough for her to get a decent meal this way. Now she takes food out of the water, and will even consume nori off the clip. She hunts pods all day long between meals, so she's getting a nice round tummy, but she still has a ways to go before she's as fat as the rest of my gang. LFSs tend to keep their fish in bare tanks and feed sparingly. Combine this with their reluctance to eat right away, and these wrasses can be pretty skinny by the time they're purchased. If you can get yours eating, expect to feed a bit more food than usual for the first while, to get him back to full health.