@JorgeB - Yeah, I was afraid of that. Curious what could have caused the partition loss. The SMART check comes back OK and there were no recent changes or power outages. I suspect that either the RAM or NVMe SSD (Cache Drive) might be reaching early hardware failure.
Some good news though, Future me had the critical data stashed away in several other areas and I'll be able to use that to rebuild my Docker images / AppData with low down time.
This time I'll verify that the AppData Backup app is installed and running - not sure why I removed it.
The other good news is this will make building my new unRAID server easier since I don't have to deal with moving the AppData from the old Cache drive.
Just setup a fresh instance on the new Cache drive and use my stashed data to reconstruct the new AppData.
Thanks for the second set of eyes on this and I feel better having verified my critical data being safe.
xDmOx's post in XFS SSD CACHE DRIVE SUDDEN ERROR - "UNMOUNTABLE - UNSUPPORTED OR NO FILESYSTEM" was marked as the answer