replying to my own comment but I'm having so many feelings about Bucky being awful and walled-off and furious in the aftermath of this, to present a tough front after being forced into such vulnerability. And also playacting normal and trying to brush it off with charm and humor, to hide that he feels so humiliated and destroyed. He's not fooling anybody, but Steve doesn't know what to do; play along? insist that he get help? Meanwhile Steve is hiding his trauma from having to witness something so nightmarish, because he thinks he should only focus on how Bucky's doing. Probably he even thinks it's disrespectful to be traumatized, since Bucky went through so much worse, or that it would hurt Bucky to be confronted with evidence that Steve is deeply not okay with what he saw. In sum, they're both IDIOTS.

-- Or, because there are so many options here: Bucky was doing the playacting-normal shtick before, and now that that's been blown up so spectacularly, he just gives up. If he can't go on how he was managing before, he feels he can't go on at all. Lets out the rage, yells at Steve that he's beyond saving so just go away, you've seen what I was so I don't know what you expect from me, sits and glares at the wall for hours and refuses to talk.