He does notice the tensing in Bucky by feel alone. Sure, he had his hand there for one reason or another, but if Bucky's uncomfortable, then he's not going to do it. Even if the tenseness lasts only a second, his friend's comfort is more important than a potential black eye.

So, he removes the hand, moving it to adjust the blanket ever so slightly, but in the end doesn't return it to it's original position against either of them.

"Do you know when it started?" he keeps his voice soft as he speaks, though it doesn't mask his concern for her. She's at a disadvantage like this, he doesn't want her to become a target for it.