Help with Shinto Ruins event

It will have it when you receive it.

That or the owner deleted the move... it's hard to tell with an in-game event on account the ID and SID are that of the trainer and not specific event IDs.

That's not true at all. Sure, they can't legitimately learn them outside the event, but they keep moves no matter what game they're sent to since this entire generation is compatible except for a few forms. The Pokémon exist, the moves exist, ergo they'll keep the moves.

That's like saying a Ralts that learned Ice Punch in Emerald would lose it when migrated to DP. Protip: it doesn't, and a lot of Pokémon used Emerald tutor moves for DP movesets.

Surely you could just trade in a couple of heart scales?

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The event moves can't be relearned or taught, so don't bother.

Oh Game Freak~...

quote w111j

Also, HG/SS does have some new moves that weren't in the previous games,

No, they don't.

The closest thing there is to a "new move" is the fact that Hypnosis got an accuracy reduction from 70 (DP) to 60 when Platinum came out.

The moves are not new. They're additions to the move pools of those Pokémon, that's it. They already existed in the previous games, and as such, Pokémon won't lose them if their traded to a different 4th gen game.