Question pages created by deleted customers

I would like to question all and any pages which might be created by both deleted customers or customers which might be not customers of the web site.

Right here is my question

$args = array(
'creator'  => '0',
'post_type' => 'web page',
'orderby' => 'modified',
'order'   => 'ASC',
'posts_per_page' => -1,
);
$posts = get_posts( $args );

I attempted to alter ‘creator’ to one thing like ‘-1’ or ‘userdoesntexist’ and none of those appear to work. I get an inventory of all pages on the web site as an alternative.