It's an optimistic little promise from the girl -- Reyes hasn't been pinning his hopes on being able to go back, though he'd very much like to, since Kadara had become a kind of home -- and how in the world would she even pass the message back to him if so?

But those aren't the right questions, and perhaps it's just the kind of joke you make to keep laughing rather than crying, so he just shoots her a smile instead. "Keep me posted," he says. as if she could.