Any chance you got the item number? If you grabbed that (or a photo of the sign), it's easy to search for it across all Costco warehouses. Query like this:

http://www.google.com/search?q=site:costco.com+576515

That will give you a list of all the warehouses that have started carrying item 576515. (It's not a new item any more, but I'm grabbing the URL from the thread in the American forum about discounted gift cards.)