[He does have a Pokedex, of course. The only problem is that he doesn't have his Pokedex here. He would ask for it back, but why would he waste an ask for his Pokedex when he could get another Pokemon back? Maybe when he had six, then he'd do it. But for now, no.

Serena might say that it's Delphox's fault, but for now, for the sake of keeping the peace, Cheren recalls Serperior. If he's there, neither of them can cause trouble, right?]

It's fine, don't worry. Some Pokemon are like that. Serperior's just... he doesn't have much tolerance for that sort of thing.