I was able to grab Mario Party and Paper Mario and get the $20. I just got this by email shortly after ordering...
This email is to notify you of a change in the release date of your pre-ordered item. This change is a result of a manufacturer decision and not Circuit
City?s, but we will keep you informed of any further date changes we receive. You will not be charged for this item until it is shipped to you.
Original Release Date: 06/01/2007
New Release Date: 05/27/2007
Product Desired: Mario Party 8 (Wii)
So there is the posibility that they no longer offer it online to control stock and ensure store availability, and they were late to fix the date. The store ad claims that you get a $20 gift card if they don't have the game Wednesday after 2pm (Just for Wednesday and I think you commit to buying the game when they do get it in)
Edit: It's $40 in store too, although the buy 2 and get $20 seems to be online only...