The Lake County state's attorney's office said the remains were found in woods about three-quarters of a mile from a parking lot where a car belonging to Nicholas Stewart was found, the Chicago Tribune reported.
Stewart, 33, of Lake Villa, vanished Sept. 20 after he talked to his boss and texted his wife to tell her he was on the way home.
A Vernon Hills police officer found Stewart's car in the parking lot of an apartment complex Thursday night, said Cynthia Trujillo Vargas, a spokeswoman for the state's attorney's office.
The identification of the body was based on "personal items that were discovered on or near the body," the state's attorney said in a statement.
Trujillo Vargas declined to say if there any signs of foul play in or around the vehicle.
The Lake County coroner's office is working to identify the remains and determine a cause of death.