Mecha Kha'Zix Skin disapeared

I had bought the Mecha Kha'Zix skin, I even played a few games with it, and today, when I wanted to use it, I found out that I don't have my bought skin anymore. Can someone help me or tell me how to get it back? I would buy it once again but then I would've payed twice for one skin and it doesnt feel right that way.