I don't think Wal-Mart has special numbers like Target does, they usually track things by UPC. So, in order to have them look something up (which they hate doing, even at Guest Services) you need to give them the full UPC number.
I can confirm this. Wal-Mart tracks all items by UPC code; in the case of Star Wars figures, each figure has its own individual listing by UPC (which is why receipts often say the name of the figure or, in some cases, names of early versions of that figure), but all ordering is done based on the collective UPC for that assortment. In the case of the Twins, if you had the UPC for each individual figure, you could look them up, or you could find the assortment UPC number, give that to a WM employee (good luck finding one to help you), and they could see whether or not the assortment was available and when it would ship.
This is also why you never see Wal-Mart clearance out one figure of an assortment if there are gobs of it. The only time WM cares about stock is when they have to reorder it, which is done by the Assortment UPC. There could be tons of Neimoidian Warriors hanging around, but if WM were to clearance them, they would have to clearance the ENTIRE basic figure line, as they come under a uniform Asst. UPC.
I don't think anyone has the UPC numbers for those Figure w/Baby exclusives yet because no packaged samples have shown up.
I haven't even seen a loose Bail/Leia set, myself. Even the Obi-Wan/Luke set from a few weeks back didn't look finished (Luke was unpainted). I'm curious as to whether or not these will hit in time for the DVD release, or if this is going to be a Christmas item coming out post-Thanksgiving.