I refuse to believe that. In the past Amazon has always extended this offer to people who already had the game ordered. I'm speaking to a rep now hoping for a better answer then that.
For some reason she said it wasn't applied to my order, but 99% of the time they say say it includes all people who have previously ordered the game, I only pre-ordered my copy on Jan 2nd and I'm positive the offer was there already. I guess next time I'll have to keep my e-mail of pre-order with the offer mentioned.
If you don't get your credit within 2 days after it ships, and you had the game pre-ordered, call customer service and they will help you out. Even if you pre-ordered before the credit was available, you should have gotten it. Just explain the situation to Customer Support.