Pretty dumb! I purchased a MBA and got the App Store gift card. Nowhere on my receipt does it say anything about the card. So Apple has no way of knowing if you received a gift card or not.
Just because it's not printed on your receipt, doesn't mean Apple doesn't know that you got the gift card. I guarantee it's noted on your account. Plus, the date of your purchase is known to Apple, and they know when they ran that promotion.
You're really grasping at straws, CPK.