If this is the one from Bluestar it should have went from Tx to Ca so shouldn't be frozen. If anything IMO it's probably a lack of oxygen. Kinda hard to say though without seeing the fish in person.
I would agree with hblue at this point. Get him some oxygenation and acclimate him.
For future reference always have a camera around so you can take a pic of him in the bag if he's dead for DOA insurance purposes.
was the WATER cold? Even the heat pack(s) are still warm, fish can still freeze to death. It's all about where you place the heatpack. Usually if body is stiff, it's frozen or on the way dying/dead