I got a skin from Riot that I already have.

So Riot gifted me the Cottontail Teemo skin. (I have no idea why) as well as Ionia Master Yi (Still don't know). I received the Yi skin but I already owned Cottontail Teemo skin, and so nothing happned. Is this a bug or something else? It was taken from iFunny because I used a round about way to get the photo since my idiotic self didn't screen shot it.