[GAMEPLAY/CLIENT] Custom item sets are deleted upon logging off

So this has happened 3 times now and is really annoying. I create my item sets for my champions, save them (yes, I do click 'save' on each), and play a few games with them showing up. When I log off and log back on later, either playing a game with one of those champions or go into item set creation to make a new one, I discover that all those sets I've made have mysteriously vanished. They're not in the game's files either.

A couple of the champions affected are currently on Free Rotation- maybe that has something to do with it?