Forcing single thumbnail to be used on Facebook with "Facebook Like Thumbnail" plugin

facebook-like-thumbnail-force-default-image-everywhere.php

<?php

/**
 * Plugin Name: Facebook Like Thumbnail - Force Default Image everywhere
 * Plugin URI: https://gist.github.com/ashfame/62f59587aaa5c8ecb1ce
 * Description: Forces the default image to be used as FB Thumbnail for every page
 * Author: Ashfame
 * Author URI: http://ashfame.com/
 */

add_filter( 'fb_like_thumbnail_shortcircuit', 'force_single_fb_thumbnail' );

function force_single_fb_thumbnail( $shortcircuit ) {
	if ( class_exists( 'Ashfame_Facebook_Like_Thumbnail' ) && ! empty( Ashfame_Facebook_Like_Thumbnail::$options['default'] ) ) {
		return Ashfame_Facebook_Like_Thumbnail::$options['default'];
	}

	return $shortcircuit;
}