Topher looks back at him when he's at least gotten some pants on. "Umm... No," he answers awkwardly. "You haven't been gone, because you were never here to begin with. This isn't your universe."

There's just really no way to break that gently, so Topher gives him an awkwardly apologetic face. Sorry, kid! You might never see your friends or family again. Have a lollipop! Except Topher doesn't have a lollipop. ...Actually, he might, but it seems a little insensitive, even for him.