Doug, with all your experience and training I'm not sure you would have found that fuse. The symptoms were no power to starter but positive on lead from the key switch and main starter breaker. Turns out there is a box with a fuse holder in it between those points, two of the possible locations are 1) above the accelerator pedal under the dash and 2) In what would be the driver's door if it had one up under the armrest but completely hidden, also inside a box which held two or three boxes. This fuse controls the transmission function which allows the engine to start.
I don't know what it would have cost for a shop to find it. IMHO the service was legendary.