Same thing, at a point in time the images are displayed to your customers,
thus they have a url in the form of <img src="image.jpg">, and therefore they can be/are linked to. That means the htaccess blocks them.
What you could do it is create a php script that will read a file and output it as a n image.
Then you could call that script from your display page, instead of linking to the images themselves.
Then you could tell that new script to only display images if the HTTP_REFERER is the display page.