Transmission Fluid Leaking problems of the 1999 Audi A8

Mine is a well-maintained, near-pristine, low-mileage car. Without warning or prior indication of a problem, the transmission suddenly ceased to operate correctly while traveling on a busy, four-lane urban highway. It resulted in the car having limited forward motion, poor control, and vastly diminished power, making it extremely difficult to maneuver in traffic. I narrowly avoided a collision with other cars. I managed to drive the car back about 20 miles to my residence in the limp-home mode--one forward gear, the engine revving between 3000 to 5000 rpm's with the forward speed no more than 35 mph. I parked the car and left it for a week while traveling. When I returned it would not move in any gear. I had it towed on a flat-bed truck to an Audi dealer. The problem was diagnosed as an inoperable, unrepairable transmission brought about when "a bolt separated from the transmission housing causing a hose to leak transmission fluid which resulted in burnt parts and gears. The cost of a new transmission was $6,800--on a car with only 50,546 miles! after reporting the incident to Audi corporate, I was informed that Audi could not be held responsible for this event because there were "no open campaigns or service actions" relative to this model. I was very dissatisfied with this response since I have been a long-time Audi owner/driver of the A8 and other models. My internet research indicates that the transmission of the A8-d2 models (1997-99) has been a very weak component part on these cars. Please help.