Well, I did come back and get it. Three SR later, and here she is. I wasn't aiming that high, but I will take it. If I use it in the story, it will be one from the story.
Btw, never leave a Magikarp like that. The bomb incident by Team Galactic at Lake Valor in Pokemon Diamond-Pearl-Platinum had my heart racing. Poor Magikarps. Poor Azelf, my favorite of the three mythical pixies.