"You seem happy.. it's good to see you smile." Sam knows. Sam SO knows. They did a whole scene just to show how totally Sam knows. Sam's so smart and supportive (and done with them.) I love it. :)
OF COURSE Sam knows!!!! It took this emotional journey for him to really Get It, but he saw how Dean’s grief operated and it was different from his own. This caused some friction between them in the earlier episodes, but he’s figured out what that difference MEANS by now. He’s on board. He gets it. He got hit by the clue bat.
I’m glad that little scene worked its way in there.