In recent days and weeks, friends and family have refocused their attention on the area between Plainfield and the Terre Haute home of his mother in hopes of finding new information that could help uncover Johnson's fate or whereabouts.
Friends like Indiana State University student Monique Iverson believe it is possible someone in Greencastle or Putnam County might remember seeing Johnson or his car as he traveled between Plainfield and Terre Haute.
That is one reason volunteers have expanded the area in which they are looking for him.
Iverson said Johnson's mother is a Vigo County middle school teacher who has been working with ISU students, who in turn want to offer their assistance in the case.
A 5-foot-8 black man with brown eyes and black hair, Johnson weighs approximately 155 pounds. He may have been driving a four-door white 1995 Pontiac Grand Am with Indiana license plate JS1830.
Johnson was last seen May 18 at the Value Place Hotel in Plainfield, where he left behind most of his belongings, and was last heard from by his mother in a May 20 phone call.
He needs medication for a seizure condition, which can leave him disoriented and confused.
Johnson reportedly disappeared soon after the death of his grandfather, with whom he had a close relationship. He did not attend the funeral.
To date there has been no activity on his bank account or cell phone. His phone now rings straight to voicemail.
A $1,000 reward is being offered for information about Johnson's whereabouts.
Anyone with any information in the case is asked to call Sgt. Brian Fowler of the Plainfield Police Department at 317-839-8700.