How can I teach my Pokémon a moved it skipped?

I realize that I want my Luxray to have Wild Charge rather than Discharge, because its Attack stats are higher than its SP. Attack stats, and Wild Charge is stronger anyway. However, for a reason I can't remember I skipped out on having my Luxray learn Wild Charge when it got to level 63. I went to the person who helps Luxray remember moves, but I don't see Wild Charge provided. I guess it can't remember something it never learned in the first place. Is there anyway to teach my beloved Luxray Wild Charge, or will I have to start over with a different Luxray?

I'm playing Pokémon Platinum, for DSi.

Wild Charge was introduced in Pokémon Black and White. It doesn't exist in Pokémon Platinum.