There was mention. It's mostly pretty early in TDS. Then later on when major plots are being revealed in the game. It's very subtle, but it's not like what was revealed in GTI, no. It was very much revealed though in TDS. It's not only your partner that mentions it.

@Neo Emolga well in GTI you don't have amnesia, but you aren't entirely aware of your mission. Kinda just have that vision at the beginning with nothing else to go on, but later on you find out why. You might have gotten a full explanation if not for that vision. Thing I feel that the amnesia thing makes it work in favor of the character. I still feel without that there's some odd effects that may show. A sort of "not used to this new body" effect. Though small for a short time, it'd have some small effect. I knooooow for time saving they probably do whatever game/anime does and says "screw reality's rules". It's just if you're a 5ft tall human one day for 20+ years straight. Then suddenly you wake up and you're a 1ft tall Pokémon, with fur covering your entire body, paws, a tail (especially Pikachu in this case since it's tail is what it uses to keep balance on 2 feet....or paws). I still feel aside from game/anime logic there's a lot of that to take into consideration. Let alone using the powers, though soon enough they become natural instinct. I think with the amnesia thing it all comes down to the body and mind's natural instinct kicking in. Since you're now a Pokémon and the body is entirely foreign. Yeah...I think waaay out of the box sometimes xD. More so than I probably should.