The sulk in this case is coming from loss rather than denial of her point, at least. They duck their head a little more, not about to explain on the day they're celebrating her birthday. Instead they finish another bite of cake-- their piece is pretty much gone, now, actually-- and set the fork down to reach over and grasp her wrist. "Love you, too, Misty. I'll try to think of something you can get me." They're not at all sure what that'll be, but they'll think on it.