Masteries Bug

I was playing with my friend in ranked, and when we joined in game lobby, it showed a different person's masteries, I know that they were mine, because I only had 5 mastery pages (shh, I know that's bad) and the masteries I had in game, had 16 (I think) pages, I don't know if that's happened to anyone else, pls respond rito, or someone :)