Just a suggestion, and it's not just about the sale, it's true for the everyday operation of the website: When a product is out of stock, leave the product page, but say it's out of stock. Pretty much like amazon does would be perfect (2 different pages, one is "we're out of stock but we're gonna get more" and the other is "we're out of stock forever"), but any kind of "Out of stock" page would be better than "Page not found". Removing the page entirely is a bit confusing, and the customer keeps searching because "damn it I remember I saw it at reliableguns".