Thor is watching Tony as he talks about it and it isn't altogether difficult for Thor to have some idea of how painful this might be for him. Thor is convinced that no one would or could tell him what to do, let alone stop him, but he was outside of anyone's jurisdiction. He might occasionally operate on Earth, but he wasn't from the planet. He wouldn't have accepted being bound by the laws of any other land.

"What happened after they left? You had to have found them, didn't you?"

Thor remembers with absolute clarity what Thanos had said, and Tony managed to glaze over those details. Thor needed to know.