When he steps foot through the door it's as he's slipping his cell back into his pocket. As much as he's not going to say it where anyone else can see or hear it, he's missed Cas too. But that much is obvious in the smile he's wearing as he sets his sights on the other man.
"Did I ever play you that song by Aerosmith?" He knows Cas didn't understand his reference from before, but he can probably change that by digging out the cassette he buried somewhere at the back of his collection.