How much did you pay for the car? I'd see about what it would cost to get the atx fluid analyzed to determine if he put any additive or other item to allow it to run temporarily. If you can demonstrate this, then I think you can show his intent.
He could always say the car was no longer needed and sat around all the time. So when you test drove it, it seemed fine but it was unfortunate that it gave out. to me if you can't demonstrate intent then you are outta luck. Maybe check the glove compartment for service receipts to see if the atx was being looked at or it is a long shot a quote of some type........
If you paid a couple of hundred for the car and this is the only problem, I'd perhaps get the atx replaced/rebuilt. If you are a DIY then you can save good money...I don't know what your situation is...
Bob
