Chances are he's just a very nice Pastel. It is interesting that he was sold as a normal though. Deserts are prohibitively expensive in comparison to Pastels, and are one of the more rare and desired morphs on the market right now, though there is some controversy about the ability of females to lay fertile eggs. The best I can say is that the only way to really start figuring stuff out is to breed him and see what pops up, and it seems like you're working on that now! Good luck with him either way, he's definitely one of the finest examples of a Pastel I've seen! I'm sure none of us would mind seeing some more pictures of him!
Cheers,
-Matt