I did some hunting on displaying featured images outside the loop and managed to adapt some code into a working solution. Here’s my code snippet if it’s of help to anyone else:
$thumbID = get_post_thumbnail_id( get_queried_object_id() );
if ( has_post_thumbnail() ) {
the_post_thumbnail( $picsize );
} else if($thumbID != '') {
$bkgdImg = wp_get_attachment_image( $thumbID, $picsize );
echo $bkgdImg;
} else {
[fallback]
}