Mr Thwaites then walked out onto Newton St and spotted his red Mini heading towards the Hewletts St roundabout, saying the vehicle was almost side swiped by an oncoming truck.
Mr Thwaites has owned the Mini for eight years and was "brassed off" when he realised someone had wondered down the Blackwoods Protector driveway and helped themselves to his vehicle.
He said he used his Mini as a runabout car and is hoping to one day pass it on to one of his grandchildren.
He hoped someone could spot or identify his Mini and to contact police of its whereabouts.
"There's not a lot of them around and they're getting less and less on the road. I just hope somebody lets the police know." said Mr Thwaites.