Oh, man...that's no fun at all.
A friend of mine was looking at an '83 240D, and made the 2 hour trip to see it twice. We were ready to go up there to pick it up (the seller had promised the car to the friend; yeah I know, a verbal promise is as good as the paper it's written on) when the seller told him that he had decided not to sell the car.
Unfortunately, this and a couple of other incidents turned the friend away from looking at an M-B...