The buyer pulled over again and popped the bonnet, complaining to the seller there was "something not quite right" and there was a "tapping sound", the man said.
"I was like 'oh yeah whatever that's what cars do', cars make noises you know? Like it's an engine.
"He goes around, and goes 'listen to this', and he's standing outside of the car with the door open with his foot on the accelerator going, 'can you hear that, can you hear that?'"
As the seller is putting down the bonnet, he said the man hopped back into the car "as fast as he [could]" and put his foot on the accelerator.
"Before I could even get to the front door the car was gone, and he nearly ran me over.
"I was like 'are you kidding, what the heck?' I just totally didn't see it coming, so I was definitely in a state of shock that's for sure."
The seller called the police straight away and went back to the petrol station where he had originally met the pair.
He said the couple must have driven back to the petrol station quite quickly and picked up their other vehicle.
"I just kind of sat in Burger King and chilled out for a bit. I rang my wife and I was like 'can you pick me up, my car's just been stolen.'"
As advice to other car sellers wanting to avoid his experience, the man said people should be careful and not hop out of the vehicle when driving with buyers.
"Just be streetwise and see if they're legit people when you first meet them.
"And also I'd say meet in a safe place where there are people around."
After the incident, the man said he texted the test-drivers: "can I please have my car back?" but there has been no reply.
A police spokesperson said people should take particular care when selling goods through social media platforms and online websites.
They said those planning on selling a vehicle privately should make sure they take care when doing so.
"Police recommend not conducting these sales at the seller's address or inviting someone into your own address."
Other advice they had included meeting in a well-lit area or during the day, and trading near or in front of working CCTV cameras "or perhaps by a police station".
They said people should consider taking another person with them during test drives, as well as the potential buyer.
"Trust your instincts, if it sounds like a scam, it probably is. If you don't feel safe, you don't have to continue the meeting/sale."