Kol is frantic.
He hasn't seen Elena in two days.
No phone. No text. Nothing.
Yes, they fought. But they were always back together in the next day. Or at least talking. Kol hadn't heard anything. Just silence.
He finds Caroline and hunts down Bonnie to interrogate them on Elena's whereabouts. They both told him that they hadn't seen or heard from her for the last couple days.
Kol searches the entire campus and surrounding area. He even got Rebekah and Finn on the job. To his, and everyone else's, great relief, they find her the next day. As well as some vampire the elder Salva-twit was friends with.
Elena has to calm him down when she tells him what she experienced.
(There's a brutally murdered body of one Doctor Wes Maxfield a week after)