To modify your sercrh system to find a post_id in a wp_query consult you need to this!
$args = array( 'p' => (int) $_GET['s'], 'post_type' => 'download', 'posts_per_page' => getNumImages(), 'paged' => $paged, );
It’s important to cast the String type to int type before pass the value to the ‘p’ parameter.