I got Black Alistar for one game......

I play Alistar on the occasion when I have to support. When i do play Alistar I play with the Long Horn Alistar skin, which is the only Alistar skin I own. As I load in I say to myself "What the **. I put on Longhorn Alistar " and then suddenly my friends and I in the Teamspeak start to realize that I have a very expensive(500 euro/$544 according to LOLSkin shop) and rare skin equipped. I don't know how this happened but I would like MY BLACK ALISTAR BACK. JK, just wondering if anyone knows how this happened; would love feedback. <3

Note: I checked my Alistar skins after this game and I still only had Longhorn. And sorry for the picture quality, it was taken from my phone quickly before the game loaded us in.