The Newtown Police Department is asking the public for help in locating Hoagland.
The documentary, called "Disappeared," aired Monday on "Investigation Discovery" and can be seen online.
According to police, Hoagland was last seen nearly three years ago at a Newtown bagel shop, as well as a gas station, where he purchased a map of the Eastern United States.
Hoagland, who was 50 at the time of his disappearance, left behind his wallet, cellphone, blood pressure medication, passport, cash, car and keys. He was employed at the time as a clerk at a law firm.
He has a wife, Lori, and three sons. His middle son, Max, has had problems with drug addiction and served time in jail.
According to police, shortly before Hoagland's disappearance, he was involved in a verbal confrontation in a rundown area in Bridgeport over two laptop computers that were connected with his son's addiction.
Over the past three years, additional clues have come up as to Hoagland's whereabouts. Several sightings have also been reported -- all of which have come up cold.
Police have searched the entire Newtown area for Hoagland, including Lake Zoar -- a reservoir on the Housatonic River.
Police suspect Hoagland's disappearance was either foul play or that he walked away voluntarily.
To view the documentary on Robert Hoagland's case, click here.
Anyone who has information on Robert Hoagland is asked to contact Newtown Police Lt. Richard Robinson at 203-270-4255.
Click here to follow Daily Voice Newtown and receive free news updates.