Two men were seen stealing a Reliant Robin from a street in Moulsecoomb before dumping it in a nearby park.
The pair drove off in the car after breaking into it in Moulsecoomb Way in Brighton early one morning the weekend before last.
Sussex Police said that the red three-wheeler was taken at about 4.30am on Saturday 6 April and dumped in Stanmer Park where it was found shortly before 10am.
One of the car’s windows was smashed and a door was bent out of shape.
PC Martin Rankin said: “The victim, an 89-year-old man, only bought the car in March to help him get to and from the shops as he has mobility problems and was extremely distressed when his car was taken.
“We believe whoever stole the distinctive three-wheeled car was possibly seen driving around the Moulsecoomb estate before dumping it.”
Anyone with any information is asked to call Sussex Police on 101 or the independent charity Crimestoppers on 0800 555111.