Querying post relationships in reverse direction when using Advanced Custom Fields plugin on WordPress

snippet.php

<?php
$tour_pages = get_posts(
	array(
		'post_type' => 'tour',
		'meta_query' => array(
			array(
				'key' => 'tour_author_relationship', // name of custom field
				'value' => '"' . get_the_ID() . '"',
				'compare' => 'LIKE'
			)
		)
	)
);

if ( ! empty( $tour_pages ) ) {
	echo '<a href="' . get_permalink( $tour_pages[0]->ID ) . '">Author on Tour</a>';
}
?>

This is exactly what I needed. Thank you.