Trouble using get_post

possibly:

$related_posts = MRP_get_related_posts( $post->ID );   
    if( $related_posts ) foreach( $related_posts as $key=>$value ) { 
        //only holds the following information:
        //echo $key; //the related_post_id  
        //echo $value;  //the related post title
        echo get_the_title($key);     
        echo get_the_post_thumbnail($key);   
    }

(edited after downloading and testing the plugin)