Mine has never lost any config. settings, including screen color, after a power failure (maybe firmware differences from others?).
So if you pull your thermostat off the base then replace it it will go back to previous screen settings?
What is your the firmware version?
Here mine is 1.04D. (It is under set up).
Probably first gen here as I purchased it when introduced way long time ago.
That and there are Zigbee options on the display but do not think that the Zigbee radio is inside.
Just reading some old documentation relating to the Omnistat and it does appear to have a firmware update option.
Using stats with incorrect firmware version. g! has tested firmware version 1.02c, and suggests using this version of firmware or newer. To alter firmware on your Thermostats please contact HAI. If you will be operating in Celsius your OmniStat 2 MUST be running version 1.03.