Relates a post by title.

functions.php

<?php

// Relates a post by title.
function rel_post_by_title( $title, $post_type ) {
	// If we don't have a title to lookup, then return null;
	if ( !$title ) return null;
	
	// Check if related post already exists. If it doesn't then create it.
	// Attempt to find page by value.
	$page = get_page_by_title( $title, null, $post_type );
	// Check if we have a match
	if ( isset( $page->post_title ) && $page->post_title === $title ) {
		$post_id = $page->ID;
	} else {
		// Create post
		$args = array(
			'post_status'	=> 'publish',
			'post_type' 	=> $post_type,
			'post_title' 	=> $title
		);
		$post_id = wp_insert_post( $args );
	}
	// Check if we have page ID to save, return it.
	if ( $post_id ) {
		return $post_id;
	}
}