If the PCM has gone into failsafe, there will still be codes and data held, sometimes as long as a month! If they can't find anything conclusive, I still believe replacing the electronic throttle body would be well worth trying.
You've still got warranty; Ford will pay the dealership for the repair as an attempt to resolve a difficult intermittant issue.
As a Lincoln owner, you're entitled to satisfaction. Blowing you off because "It's not doing it now..." is unacceptable.
Even this dealership wants you to bring it in "while it's still in ETC mode". HOW??? In ETC Fail, the car is locked at idle speed. It's barely driveable!
It sounds to me like you're having major problems finding a dealership that will even make an ATTEMPT to resolve your problem. Before your warranty runs out, call:
Ford Motor Company Consumer Relations
1-800-392-3673 (1-800-392-FORD)
Have the names and addresses of the dealers you've seen, the dates of the visits you made, and, most importantly, the work order numbers of any work orders relating to this problem, even if they say "no fault found" or "unable to duplicate".
You do have work orders, don't you? The dealers didn't just blow you off at the door or over the phone without even trying to figure it out, did they?
If so, go to a dealer and demand that a work order be written and the car be brought into the shop.
Ford won't be able to assist you if you have no proof you were ever even near a dealership with this problem.