So I called Amazon since the "how to" says: "Customers who have pre-ordered FINAL FANTASY XIV: Heavenward will receive an 18-digit pre-order code (hereafter referred to as the‘pre-order code’) from their retailer."

Fantastic customer service! Turns out the Amazon has been having delay problems with getting the pre-order codes out. If you're having similar problems, I suggest contacting Amazon to verify this. See you in game!