On the afternoon of Wednesday 25 August 2021 the victim, a man in his 60s, agreed to give the suspect a lift to Ashford in a blue Volkswagen Polo.
While travelling on the A251, towards Ashford, the suspect is said to have assaulted the victim.
The car subsequently stopped in the middle of the road, just prior to the M2 slip road for junction 6, and the driver got out upon being threatened by the passenger.
The vehicle then drove away and investigating officers located it in the Lydd area that same day.
As part of enquiries, a 52-year-old man from Romney Marsh was arrested on suspicion of robbery and he has been released on bail, pending further enquiries, until Friday 17 September.
Investigators believe there are motorists who may have observed the offence take place, or who captured the blue Volkswagen being driven on the A251 between 4 and 5pm.
Anyone with information is asked to contact Kent Police on 01795 419119 quoting 46/157012/21.