[CLIENT] Need to rebuy the Champion(already bought it 2 times now)

Hi all, This bug is a bug that impede me from enjoying the game. I hated it! Two month ago, I want to play Ganr. But It shows ar unowned(I am pretty sure I bought it). As a result, I bought it again. Two days ago, I was going to buy another champion, and I found my gnar display as unowned champ AGAIN! This time, it come clear to me there is a bug happened. We all know that you can't have a chest unless you owned this champ. So I definatly owned this champ once before, since I had a chest (see the image) and .... yea it doesn't belong to me anymore. I believe same thing happened to some of my other champions. Mordekaisar for example. (I did bought all champ under 4800ip back then) SO, RIOT, PLZ HELP ME! Sincerely! id: Dashuai1