Lost Champions

I noticed that recently, I have lost two champions. I don't know if those were the only ones that I lost but I did notice that Vayne and Kalista weren't in my list of champions anymore. I noticed right away, because I played them a lot, and bought them with RP. I don't need a refund or anything, but I need the champions back, since I really want to play them again, and I don't have any RP or IP left. Hopefully Riot will fix this bug of losing champions. I've read in other spots that others have also seen this problem. Riot, please fix this