Hi,
On a products listing generated by HikaShop, HikaShop will only display the products accessible to the current user.
So this situation should normally not happen in the first place unless you've customized HikaShop in some way or there is some interference with a plugin, etc.
If you want to redirect 404 errors to a special page, you can use the redirect system of Joomla:
www.templatemonster.com/help/joomla-3-x-...-component.html#gref