Skins Missing

So, a few weeks ago I was mystery gifting a friend and I received Snow Day Ziggs and a Ryze skin (I believe it was Tribal Ryze). I liked them and played many games afterwards with the Ziggs skin (not with Ryze, but still it was available). I kinda stopped playing as Ziggs because I was playing badly as him, but about a week later (this would be yesterday) I was looking to play him and the skin was gone. I mean it is just straight up not on the Ziggs skin list. I checked with Ryze and, sure enough, that one is gone also. I would really like to have them back, so if this could get fixed or something I would be grateful. Thanks.