I would offer the following based on very recent experience
and suggest you don't get too wrapped up in troubleshooting until everything thaws out.
We are currently in Pueblo, CO. and it got cold quickly and went down to about -4 a couple of nights ago, only something like 16 for a high yesterday.
I got caught ... water system froze up, first shower lines and then water to kitchen and blue room. Shower lines have frozen before (last year) but first time everything froze. Pump didn't run either, gray and black tank indicators indicated empty although I know there was some since we dumped a couple of days before. Waste tank heaters have been on since before it got cold.
Pump and water tank are inside, under the bed so wasn't too worried about that, remote thermometer confirmed it is staying in the 50's in there.
Put a cube heater in pass through compartment by the water panel and brought temp up into 50's. After about 12 hours lines to everything but shower opened up, pump operated normally, even though it was still well below freezing outside. (Pump didn't operate while line was frozen because there was pressure in the line already.)
Today it warmed up into the 40's or more ... shower lines thawed out, tank indicators are indicating normally again.
Haven't been able to figure out where the shower lines are freezing or I would put some heat there. For now plan on keeping the cube heater in the back compartment now that I know that is a problem area. Don't have a drop light to try at the moment but may get one to try and monitor with the remote thermometer.
So while I understand your concern get the system thawed before you get too concerned about tank indicators or pump operation.
Hopefully neither of us will have any leaks.
And yes Ron, I do know the preferred winterizing method ... just can't leave quite yet!