AX4N transmission

I had a funny thing happen to my ford taurus transmission. I was told by a nice passerbyer that I had a fluid leak. Sure enought i did it was transmission fluid. I zoomed home and turned it off. There was no leak at that point I thought it was out of fluid of teh transmission. I then added 6 quarts to the transmission and restarted the car. Now there was no leaks. I test drove the car very hard and still no leaks.

The history of the car is that it has 197k miles on the engine. The transmission was replaced at 105K miles and have never had a problem.

Has anyone else seen this problem ? if so how did you fix it.