Okay, so when the spring event ended, I had only needed a couple of topazes and one pigment to be able to craft the unicorn outfit. Then, when the event ended, all copies of the design left my inventory and my library... which was expected.. the event ended after all. I was browsing the item trades all dissapointed about that... then all of a sudden, I came upon an extraordinary item exchange. The person was offering a scheme/blueprint for the dragon festive outfit. Weren't those supposed to be gone? I accepted the trade offer thinking, ''what the heck, it'll probably disappear in my inventory...''

I checked my inventory. The scheme was there. I used it - put it in my library. Thinking it would disappear by now. It didn't. It was still there.

I had all the materials needed. I could craft the darn thing. So I pressed the crafting button. And it let me. It let me craft the outfit. IT LET ME. Is this supposed to happen? 

Thank you for reporting!

Probably the script that should cancel recipe auctions and destroy the schemes didn't work properly. The bug is fixed, all recipes are destroyed now for sure. You may keep the crafted outfit as a reward for reporting this bug.