Well, I never did find where fused power to the water heater comes from, but in hopes that this might help somebody else in the future...
No 12v power to the water heater control board, but I pulled the switch panel and 12v was present there. Interestingly, none of the wiring to the switches matches the size (or even color in some cases) of the wiring in the water heater connector (at the control board). I found that by pulling an access panel inside a cabinet, right above the master storage light shutoff switch that all the wiring was exposed. The wiring from the switch panel is spliced with wire nuts to a pigtail coming from the water heater connector, apparently one or more of those splices wasnít solid. Bottom line, my water heater is working now. After this trip Iíll probably pull that panel and replace all the wire nut splices.
I would still appreciate knowing where that fused power comes from though...
2014 Newmar Bay Star 3124
2015 Ford Edge Titanium