I just called Costco to see if they had any deal, and I found out you are routed back to Disney. So you are actually talking with Disney Directly anyway. They said sometimes Costco does offer a gift card, but not currently.
Yes, I've called the Costco number twice to book and it goes directly to ABD. Even when my trip was cancelled and ABD called me and rebooked my trip they made sure I got my Costco gift card. That's disappointing to hear that they're not currently offered. Did you specifically ask about 2010 itineraries? They still have the gift card promotion on their website for the remaining 2009 itineraries (some of which are actually in early 2010). I've received gift cards both times when I've booked through the Costco number and I think that's been the experience of all the other folks on the board too. I hope this isn't a permanent change. Makes the Dreams Unlimited offer look good though.