Disabled driver Anne Toomer could only stand and stare when thieves sped off in her car after taking it for a test drive.
Mrs Toomer, who has back problems and uses crutches, travelled as a back-seat passenger while the couple took the car she was selling for a spin.
But when they returned to her home in Ashington Gardens, Peacehaven, they told Mrs Toomer they would like to have a look at the engine.
The man, who had been a passenger while the woman drove the white L-registered Ford Fiesta, got out to open the child-locked back door for Mrs Toomer, 59.
And while she was organising her crutches, the couple took their chance and drove off in the car, which Mrs Toomer had been trying to sell for £1,500.
Mrs Toomer said: "I just stood there like an idiot.
"They had gone up the road almost burning rubber. I could not believe it. I stood there flabbergasted.
"You just do not believe anyone is going to do that.
"I walked back indoors and said to my daughter, 'I think they have stolen the car.'
"It has quite thrown me. I felt quite shocked and a little bit tearful."
The man was white, in his early 40s, 6ft, of thin build, with thinning short hair. He was wearing casual clothes.
The woman was also white, in her late 30s, with brown mid-length hair, of slim build, 5ft 3in and wearing a light-coloured skirt and a stripy top.
Mrs Toomer said: "They seemed such an ordinary sort of couple. They asked if I wanted to go with them. That lulled me into a false sense of security."
Mrs Toomer, whose daughter and son-in-law Sue and Lee Winchester live with her, also had to have the locks on her council house changed because her house keys were on the same key ring as the car keys.
The theft, which happened after 1.30pm on Tuesday, was reported to the police.
Officers searched the area for the car, which has now been marked as stolen.
A police spokesman said: "As the caller was on the line, a unit was being told about it. We were given details of the suspects.
"It is obviously unfortunate that she has been a victim of crime in this way and we will do all we can to try to recover the vehicle."
The car's registration number is L787 MKX. Anyone with information should call Sussex Police on 0845 6070999.
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