All Jace had been focused on was getting him and Alec away from Valentine. He had not meant to portal them to a different space. Stuck, and now having to figure out how in the world they were going to manage to handle a totally different time without being too suspicious, and help with this clock issue they have going on, Jace and Alec are already dealing with enough. Not to mention the recent torture Jace suffered at Valentine's hands, and the skewed mental state for both of them, it would be a miracle to get out.