Steve doesn't say anything right away. He works his jaw, betraying his frustration with his inability to find Bucky on his own. It passes after a minute. In its place the obvious questions start flooding into his head. They have hours to go. It's more than enough time to reflect on how they got here in the first place.

"Why were you looking for him?" He knows it can't be revenge. If Tony wanted to kill the Winter Soldier, he wouldn't have brought him along. Tony is a lot of things, but stupid and cruel are neither of them. The other possible reasons escape Steve. As far as he can tell there are no more things to motivate Tony to help with the search.