"Alchemy is a science. It's based on strict scientific laws and principles." She wasn't the first person to make this mistake. Hell, people from Amestris tended to jump to the conclusion that it was all magic, and since she clearly believed in that mumbo-jumbo, he's not surprised at her confusion.

"As much as I wanna help, I've got to get back to Amestris and take care of some business." He turns to leave, but realizes that he has no idea how to get back. "You wouldn't know where to go to find out how to get back where we came from, do you?"