I finally e-mailed them to ask where my magazine was, and this is what I got back:
Due to high demand, we were unable to fulfill all requests for this offer. If you have not received anything, it is possible that your order was unable to be fulfilled.
The order-tracking system on our website is for paid magazine subscriptions only, which is why no orders were found for your email address.
Thank you,
Subscriptions Plus
So, it's not looking good, and they're not letting us know whether or not we'll be getting it.