Kalogerakos was last seen by his roommate, Mike Dauber, in Idaho City, Idaho on December 28, 2007. His roommate met with him at the Hilltop Cafe along Highway 21 and asked him to move out of their trailer. He has never been heard from again. His mother and sister in Chicago, Illinois reported him missing after they hadn't heard from him in a week; prior to this, he had daily contact with them. Kalogerakos may have been seen in Boise, Idaho after his disappearance, but this is unconfirmed. He had moved to Idaho three months before he went missing.

Kalogerakos told his family he had been fighting with his girlfriend and Dauber prior to his disappearance. He left behind all his belongings and his car. He supposedly signed the car title over his girlfriend, who then whited out her name on the document and gave it to Dauber.

Curiously, Dauber also knew another man, Joshua Reddington, who disappeared from Idaho City in 2000 and was never found. Dauber was the last person known to have seen him. Authorities haven't said whether they think the two cases are connected or whether Dauber is a suspect in either of them. He now lives in Texas.

Although there is no indication of foul play in his disappearance, authorities believe he may be dead. He had only lived in the Idaho City area for about a year prior to his disappearance. His case remains unsolved.

Some agencies give the date of Kalogerakos's disappearance as December 25, 2007.