From my understanding (and I'm not involved in the shipping of stuff so I can't say definitively) the two sites are independent of each other so there is no cross referencing between the two. Sort of like if you were to buy something off the Sears site and Kmart site and want them to combine. They are both part of the same company, but they are independent of each other. (Not a real great example, but I think that's the gist.)