It is.
Blizzard have just become too lazy and greedy and rely on their stupid website now that doesn’t track half the items you get rid of and only has a limited time.
Before this dumbass website was a thing and Blizzard had actual humans working for them they would check if you had indeed completed the quest, and give you back the key regardless of the timeframe.
You’re out of luck now though, OP.
It’s very possible and should only take like 2 minutes max, but GL getting blizzard to do some effort kekw.