Hi,
Unpublishing products won't remove the products from the search results immediately. It requires search engines to recrawl the pages to see the 404 error.
Also, this doesn't look like a Joomla 404 error page. 3 years ago we made modifications to the product / show.php view file to properly display 404 pages for products not found:
www.hikashop.com/forum/product-category-...g-with-hikashop.html
If you have overrides based on older versions of HikaShop, you might now have these changes, and thus that would explain why it's not a real 404 error page.
For example, if you access
mywebsite.com/test
(of course, you need to replace mywebsite.com by your website domain) you'll see a normal 404 page and that's what you should normally get. This is necessary for search engines to understand that the page doesn't exist anymore.