bp_get_attachment_media_id( integer $attachment_id )

function bp_get_attachment_media_id( $attachment_id = 0 ) {
	global $bp, $wpdb;

	if ( ! $attachment_id ) {
		return false;
	}

	$attachment_media_id = (int) $wpdb->get_var( "SELECT DISTINCT m.id FROM {$bp->media->table_name} m WHERE m.attachment_id = {$attachment_id}" );

	return $attachment_media_id;
}