Sam never could hide from Dean. Which was usually a good thing--even if the muffled sound of his brother pounding on the door shouting his name in the hallway made Sam cringe at the answering pounding of his head. He felt hungover, but he was pretty sure it was just the fact that he hadn't been sleeping well.
He didn't yell back. He just got up and trudged over to open the door. If Dean asked, he'd pretend he was hunover.