Post Template Query with WP_Query?

If you are still stuck, one possible alternative is to get all Post ID’s by the custom post type. You could try something like this:

$the_query = new WP_Query( array(
  'post_type' => 'my-custom-post',
  'posts_per_page'  => -1,
   )
));
while ( $the_query->have_posts() ) : $the_query->the_post();
    the_ID();
endwhile;

It would require you creating a custom post type, and associating posts to it.

There are ways you can associate page templates to posts, but as far as how WP_Query would work from that point with that process, I still have to learn 🙂