Check Engine Light On problems of the 2011 Ford Flex

I have full documentation from Ford to back up my story: last year the car began stalling intermittently. In buffalo, NY (we live in the chicago area). The stalling got so bad that she was worried about driving back home 10-hours+. She went into the local dealer there and had the car plugged into the computer. . . Which detected no faults. She made sure to describe the problem fully and it is documented on the receipt. The car has continued to have this problem. I read that the Ford dealer can install a "black box" with a button that one can push when an intermittent problem happens. We did this and we got three good pushes of the button when it subsequently stalled and the dealer downloaded the info and found that the throttle body is faulty. . . . Of course the car (we had extended service plan) is now out of warranty for about 1. 7k miles (not time). Note that the car failed to trigger the check engine light. . . It was only at my insistence that they put in a "black box" that any problem was found. The Ford customer care person on the phone keeps telling me that "the current problem" occurred after the car was out of warranty. But our documented maintenance history proves that this is a problem dating from last year. This is a year-old problem that the dealer was only just able to diagnose. . . And then only because I learned about the "black box" that was available. The bottom line is that the dealership failed to find the problem last year, and because they failed to find the problem we are now on the hook for the repair. I have copies of the receipt from last year. Oh, and to add insult to injury my wife had to pay Ford $108. 70 for them to plug the car in last year. . . The car never had a check engine light or displayed fault codes when plugged into the computer normally. It would have been nice if the black box was suggested as a diagnostic option however.