On my old 1999 F250 V10 I had 2 coils go bad. I was the culprit as I washed the motor and the boots around the coils were bad and cracked. The water shorted out 2 coils. Even with 2 down the only way I could discern the issues was to replace a coil and then take the truck for a ride as it would only miss under a load. The cause of your problem sounds different but it is likely the same result. In my 1999, it didn't set a code or even light the SES light. If you want peace of mind, replace all the coils along with the plugs and foam rubber boots. Have your mechanic put a dab of dielectric grease on each boot to help it seal and make removal easier next time.