Failed to operate at all...
I forgot to consider that I did clean the weapon after her last outing; but no way would I have locked the trigger mechanism. The two keys were still sealed in the factory bag, and I would have had no reason to do so. The gun lives in her purse during the day, and on the nightstand at night.
But, this does raise another possibility that the lock mechanism somehow engaged during re-assembly, but I don't see how.
Lesson learned, and shame on me- for not checking for proper function (dry fire) after cleaning and re-assembly.
Not sure that I'd get a straight answer from Ruger if I called (this would be a defect) to ask if they are aware of circumstances where this could happen but I'll give it a shot.
Meanwhile, I'd still be interested in hearing from anyone with the necessary smithing knowledge capable of studying the schematic and the workings of the mechanism as to whether they feel it would be possible for that safety to rotate the necessary 1/4 turn to disengage the trigger, without the key provided....