I would start a search for his body, on grounds that if he had a disease, it could be passed on to other fish when they pick at his body. Before completely tearing apart the tank, I'd look around the floor to see if he has jumped. Also, check in caves, I've had a few pass away in there before. Finally look in the plants, a few bad experiences there as well.
One other question is do you know WHY this fish died? Were there any spots on his body, any other signs of somethign that was obviously wrong? What are you water stats? ammonia, nitrite, nitrate, ph, and temp? Those can be useful to in identifying what went wrong.