Actually, I tend to believe the dealer. I've been haunting several of the Ford forums, and many confirm the same thing. The Wrench ("limp home mode") by itself doesn't produce stored codes. Only if the "Check Engine" comes on will there be something afterwards to find. I'm thinking of the Torque Pro app, but being an iPhone/iPad/Windows household, that also means buying some Android device. I'll look into Ultra-Gauge.
Two of the times it happened, it was right at startup. Hadn't even shifted into drive. The third was while waiting in a line of cars to take their turns at a stop sign. No warranty. Have about 60K on it currently. There are a bazillion ways for something to go wrong and give the error - dirty or bad throttle body, intercooler issues, the fix due to water build up, etc., etc.
I'll go on the trip. Guess we might see how well CoachNet really works! Also have AAA just for the truck. It's all about the adventure, right?
As far as premium, I've found that it does give about an 8% boost in mileage. So for daily driving, or short trips with the 5th, I'll use regular. But for cross country hauls and/or where stations may be fewer, I'll go with the expensive stuff just to get a bit more range out of it.
2012 Ford F-150 Eco, Max/Max
Jayco 26.5 RLS, Reese Sidewinder