Engine Stall problems of the 2008 Mercury Mariner

I was driving on highway route 22 at approximately 60 mph, when suddenly the throttle stopped responding and the tachometer started dropping. In a matter of seconds the tachometer reached zero and the vehicle stalled, while I was in traffic on the highway. I coasted off to the shoulder and put the vehicle in park. When I tried to restart the vehicle, the engine would turn over and start up, however, immediately after I let go of the key, the tachometer would drift back down to zero and the vehicle would stall. After a few more failed attempts, I called for a tow. Since this occurred after hours, no one was available to work on the vehicle until the next morning. In the morning when I attempted to show the technician the failure, the vehicle started up as it did the evening before, then the tachometer started dipping back down, then just before it stalled, the tachometer fluttered a little, then the engine revved back up and began idling normally. The technician indicated that there were no events logged in the vehicles computer to give him an idea of what caused the sudden stalling, and he could not find any obvious issues with the vehicle. The vehicle was returned to me without repair and the technician warned me that it is likely that this would happen again and that they cannot diagnose it unless they see it when it is not working. Now I am concerned that this will happen again while driving and that it will cause an accident, or worse. I read an article from the north carolina consumers council stating that there is a known issue with the throttle body of this vehicle that causes sudden engine stall while driving. Ford issued an extended warranty on certain vehicles for this piece, however when I contacted the dealership and mentioned consumer satisfaction program 13n03, they informed me that my vehicle did not qualify. I'm not sure what to do next.