Hi,
I'm not able to reproduce the problem.
You can test on our demo website. All the products display on the backend products listing, regardless of their quantity or if they are published or not, or if they have an image or not.
There is actually no option to not show them.
One reason I could see would be if you were using a custom plugin implementing the onBeforeProductListingLoad trigger without checking whether you are on the frontend or the backend with such code:
$app = JFactory::getApplication();
if($app->isAdmin()) return;
In that case, the plugin would remove from the listing in the backend the same products it is removing on the frontend.