Suddenly all my files are gone - 1.5 TB lost

So I checked everything, the notifications only indicate that there has been a successful firmware update in the meantime. 

What, between you upgrading the software and your data going missing?  Is Firmware Auto-Update enabled (it might have been enabled when you did the system restore…)

I note that a firmware upgrade was announced yesterday; is this the version you now have installed?

http://community.wd.com/t5/WD-My-Cloud/New-Release-WD-My-Cloud-Firmware-Release-4-01-03-421-2-23-15/td-p/859053

Interestingly, my MyCloud is only telling me that there’s a 4-01-02-417 upgrade available…