Hextech Crafting Bug

I unlocked 2x Definitely not Vel'koz skins despite having other skins I can unlock. I believe this may be a bug in the hextech crafting system.

At the time I had all champions bar Vel'koz and all the hextech craftable skins bar the list below;

Hextech Annie Gravelord Azir Lunar Wraith Caitlyn Jade Fang Cassiopeia Headmistress Fiora Pool Party Graves Shadowfire Kindred Elderwood LeBlanc Woad Scout Quinn Championship Shyvana Battlecast Vel'Koz Arclight Vel'Koz Officer Vi Special Weapon Zac Pool Party Zac

The chances of glitch replication would appear to be sufficiently low on other accounts that it will likely be that not many other people will encounter it. The chances of occurrence on my account was 1/16 at the time.