As distracted as he might have been, Snow wasn't so bad off that he didn't notice when the door opened and someone walked in. But he was evidently bad off enough that he didn't immediately trust his eyes. He glanced up, prepared to offer a half-hearted glare at the nurse, and ended up doing a complete double take at the boy's face. He actually gaped for a second, then suddenly looked exceedingly confused.

"Izaya?!" He stared at his face, then at the door, then at his face again. It was pretty evident he was wondering if he'd gotten shoved into the wrong room. "What're you doin' here?"

...Snow actually glanced around the room himself for a second. Maybe he was the one who'd walked into the wrong room.