I have heard of a switch or solenoid causing this issue, more likely something of that scale than a fault with the gearbox itself.
Question is - what does the AA patrol do to get her going? Just clear the fault code? Sensor faults will often log a fault code that is not serious enough to illuminate the check engine light. If you can identify that then the fix should be reasonably inexpensive and swift.
An ELM327 OBDII bluetooth adapter hooked up to a smartphone with an app such as Torque is handy in these circumstances.
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TG