"I don't think it's impossible."

He isn't saying it's possible, either. In theory, he assumes so unless proven otherwise, but this world is still quite a mystery.

"The answer might be hidden in these books. There might be a map or mention of visits to the other places."

Or tacky romance books.

"When we go back, we'll write about this place. If those aren't hidden, that's how the next group will know this town exists. Somebody might have done the same here."