It is available for pre-order at Amazon.com.
Amazon uses a "pre-order" sign-up system where you can be notified when certain items become available.
Having several pre-order dates will reduce the strain on the support systems and technology frameworks of manufacturers.
Just about every major retailer offers you the ability to pre order video games, but not all video games will be available to preorder at each retailer.
There is a chance you may have overlooked the sheet that came with the pre-order information, but that's okay, there is no expiration date for this offer.