So had done a little research yesterday, but thing is I was having difficulty finding one piece of the puzzle. Have you confirmed that the 302 followed by 404 occurs even as the first visit to the site? I ask because of some of the standard operations that occur.

Generally speaking I found only two places that really addressed the "missing product" condition. The first that a guest is expected to come across is the sanitizer. But the conditions of the sanitizer appear to not play a factor on first visit, though I didn't look to see if the sanitizer is double run by ZC. So, if run once per "page" load, then on first visit it sets a session variable that would be used later to do a different action.

The second place found as related to the specific url provided was the header_php.php for product_info (includes/modules/pages/product_info/header_php.php) where the "first" line checks if the product exists and if not modifies the header to provide a 404.

So then, one asks, so whee's the 302? Well, a header sent with a location like is used to redirect will without other direction issue a 302 based on the php.net documentation on the header function. But, in the above process of establishing a "first" visit or as seen/detected by a SE which is not supposed to get an established session, there does not appear to be an action that would so automatically issue the 302 (no redirect action that would do/cause that). The only thing that appears could cause a 302 to be issued with a 404 in a non-session based visit is settings on the server that issue a 302 when a 404 is issued which based on the limited read of the php manual on the header function are either server based or controllable by the php.ini.

In summary, a "white-hat" SE or a recognized one will not start a session and therefore will not see the 302 of a redirect because of a non-existent product, but instead see the 404 as provided by the settings of the host server making the 302 followed by 404 a non-issue for such "visitors" but instead something seen by those with a session like a browsing customer.