[James doesn't reply at first. He knows Sirius said it. He could see his mouth move and he's positive something was said, but the word is gone. It will be weirder if he calls attention to it, he thinks. If he says "Right! That!" without repeating the word himself, it will be obvious something's wrong. Though, that might be obvious now, since he hasn't said anything.]

...The longer we stay here, the more difficult it's going to be, I think. But I don't think it will be impossible.

[He's already forgotten some things, but he'd gladly forget half his vocabulary if it meant they could all live happy lives.

He's glad Sirius made that move though. Hoping to distract from the awkwardness of all this, he slides his Queen out of hiding and snatches Sirius' bishop with a sneaky grin. Not only does it take away one of his more powerful pieces, but it puts his knight in danger.]