Random fun fact for laughs:
Early this afternoon, I logged in to grab an Enchant Key and had it in my cart, but got pulled away before finishing the transaction. When I got back, it put me in the queue again. I didn't have time to deal with it, so I closed it out.
By the time I got back into the queue late in the afternoon, Believe was already sold out. And then Enchant sold out while I was in the queue. (Honestly, I was more gently-bummed than disappointed.) So I closed it out.
Just out of curiosity, I went back into the site about an hour ago to see what things looked like.
After going through the queue and logging in, I was shocked to see that the Enchant Key was still in my cart. The site was misbehaving at that point (in Firefox), and it wasn't letting me go to Checkout (just looped me back to the Cart), so I assumed it wasn't going to happen.
On a lark, I switched to Chrome. When I logged in, it was
still in my cart. And, insanely, it let me check out.
So, at risk of stating something either useless or obvious: it turns out you can actually buy a sold-out Key if it's already in your cart.
Honestly, a nice surprise at the end of a weird day.