Sam heard the frustration in Dean's tone. He considered asking but assumed that he'd hear about whatever it was soon enough.
"I'm okay," he said. "I've just been trying to figure out what the key goes to. And I've found it."
He looked around, trying to figure out how to put it into words. Eventually, he decided that this was sort of a 'seeing is believing' type of thing. And he really didn't know what to say about their grandfather, though that was something best discussed in person.