Wordpress 'post_type_link' hides permalink

PHP Snippet 1:

function append_id_string( $link, $post ) {
    $post_meta = $post->ID;
    if ( 'product' == get_post_type( $post ) ) {
        $link = $link . '#' .$post_meta;
    } 
    return $link;
}

add_filter( 'post_type_link', 'append_id_string', 1, 2 );