Peeta's brow pulls into an expression of confusion, one of thought. None of what Katniss is saying makes sense, but at the same time, he trusts her and knows she's telling the truth.

"How is that even possible?"

They'd been led to believe that Panem was the world. At this point, he's accepted that there is so much to the world than Panem, but the idea that Panem isn't even mentioned is mind boggling to him.