I used the wall cheat to get past Flutteryay's barrier and continued on to Mt. Moon just to explore a bit more, so that could easily be the reason why this happened, but it's still extremely weird. I was leveling up my F Bon Bon in the in the room with TM 46, and the Team Rocket Grunt. I fought the Rocket Grunt, and F Bon Bon hit level 22, and she evolved into Bon Bon. I went back up the ladders to the entrance floor, and continued on my way. I get into a battle with the next Brony I came across and now it says my Bon Bon (still evolved), but she's instead at level 19. I'm really confused by this. I'm going to try recreating this to see if it was a freak accident, or if it was just going into unfinished territory. It seems like the type of thing that should be brought up to someone's attention, so that's why I'm explaining it in this blog post.