Damon had pretty much spent the entire time since Elena had disappeared drunk. He'd concentrated on comforting Elena after Bonnie had died. But, once Elena had gone, he'd let himself feel her loss as well as Elena's. And, with Lexi gone, he and Stefan had gone out and gotten completely wasted. And this, was why he was passed out on the couch that morning, and not in his bedroom.
But, he soon woke up when he heard Bonnie's voice. At first he thought he was dreaming. That he was still asleep. But, then he heard Caroline's reaction and he knew that she was here. That she was back. And, even with Elena gone he couldn't help but smile. And, within a flash he was stood leaning against the wall as Caroline was obviously trying to squeeze the life out of the little witch.
"Careful, Blondie. You don't want to kill her again."