Probably would be a good idea too to snap a photo, printout, write down, etc., the SKU and UPC/BAR codes, price and quantity of the item(s) you're searching for that Brickseek shows stock in and have it with you when visiting each Walmart or any of the other stores that the Brickseek website covers as it could maybe help track if the item has been legitimately sold or "disappeared / can't find".
On ATF critical items such as modern firearms I would think the "disappeared / can't find" response would be a MAJOR no-no and should trigger an immediate search.
