Pokémon Sun and Moon - The whole reason for the plot

next visit to Poke Pelago
"Get your ass back to Aether Paradise, you bean-munching beach bum. Your family nearly fell apart while you were away, and Ultra Beasts almost overran Alola because your wife went batshit insane. And now she's essentially hospitalized for neurological damage."

Well, as far as I know, he could have lost his memory after the events, which would definitely explain him being in the Poke Pelago…