I forget where it was I read it, but in one story, Pierce gave the Soldier specific orders to scream and show pain and fear while he was fighting Captain America, just to screw with Steve. I feel like this could totally work here, like, Steve heard the way Bucky screamed when he dislocated his shoulder on the helicarrier, so he doesn't even consider that Bucky would be burying his distress later on.
Re: Bucky has been conditioned to not show any outward signs of fear or distress