OK from my understanding:
1) The deal was POPULAR!
2) It was also SO POPULAR it CRASHED the authentication server!
So seeing them cleared out seems legit(another person in checkout next to me was getting one as well), and the crashing bit doesn't surprise me(I guess the thing didn't like the sudden surge in Amazon GCs and all that holiday in-store traffic...).
The guy at checkout (who told me about #2) wanted to do a rain-check since they can't activate it, but the manager wouldn't allow it.
This is the first time I have had this happen with their promo codes involving gift cards, so I'm not to sure they bulked and cancelled it/purposely removed all the cards/etc. Maybe at some stores they did remove them so customers wouldn't bother trying.
Meh, the line wasn't too bad, but I'm not even sure I want to bother trying Sunday when they open.... Tuesday is the last day for this deal and who knows if there will be any cards left by then.