said by psafux :

thanks for the reply. I have turned off every other breaker, short of the MAIN, and everything in the bathroom remained on, and 4 volts still registered at the switch in question.

Breaker #15 is the only circuit that turned off the bathroom in its entirety.

If I understand what you are saying, this would have ruled that out ?

Also - this morning I tested hot-ground, hot-neutral and both registered 4 volts. I am testing the wire not the terminal on the switch.