Hextech crafting bug???

Riot said "you can re-roll a skin shard with three others for a shard guaranteed to be for a champ you own". I just re-rolled 3 skins, and i got a malzahar skin(wich i dont own the champ). WTF? I dont own malz! Is this because of the weekly rotation? Because i'm kinda screwed right now. Plz help