I had exactly the same problem with a Focus I had.
It had stood on my drive for 8 months undriven (apart from when it went for its MOT 2 months before) and was covered in bird****.
Anyway, I had some bloke knock the door asking if I wanted to sell it and he offered £1500 for it. At the time it was worth probably £2000 but for the sake of having to get it valeted and all the other stuff I took the money.
He was the same, test drove it etc. He came back 2 weeks later telling my other half he wasn't happy and it was making a funny noise on the gearbox and his "mate who worked for Ford" said it needed a new gear box.
He got the royal F*** right off from my other half and told he'd test driven it etc etc and it was sold as seen. He buggered off and we never heard from him again.
Fingers crossed the same happens to you and you don't hear from him.