BP_Messages_Thread::get_messages_count( int $thread_id )

	public static function get_messages_count( $thread_id ) {
		global $wpdb;

		$bp = buddypress();
		$thread_id = (int) $thread_id;

		if ( ! static::is_thread_recipient( $thread_id ) ) {
			return 0;
		}

		$last_deleted_timestamp = static::$last_deleted_message? static::$last_deleted_message->date_sent : '0000-00-00 00:00:00';

		$results = $wpdb->get_col( $sql = $wpdb->prepare(
			"SELECT COUNT(*) FROM {$bp->messages->table_name_messages}
			WHERE thread_id = %d
			AND date_sent > %s
		", $thread_id, $last_deleted_timestamp ) );

		return intval( $results[0] );
	}