When Sam touched his shoulder, Dean's eyes turned and focused on his brother. Leave it to Lexie to do the "right thing" and alert his brother that things were dire. That something unpleasant had happened to Dean Winchester. And yet, he wasn't upset about it. There was something important about Sam coming to see him so immediately after a catastrophic day like the one he'd had. Sometime very important.
"Did you know," he asked with a slightly dreamy smile as he gazed up at Sam. "Every happy memory I have includes you, Sam? That's sort of funny, isn't it? Not funny ha-ha but kind of funny strange. I never noticed it before now. But you're like my good luck charm where happy memories are concerned, dude."
His eyes went out of focus again as he stared off into the evening sky again. This time to be washed in thoughts of playing cards with Sam or learning to shoot and almost having his head taken off by his little brother. The heap of laughter they'd landed in afterward had been fantastic. Dean practically beamed, ignoring Sam's questions.