I am wondering if this issue has anything to do with the addition of OneDrive to the Storage Sense utility (Settings->System->Storage) in the October 2018 Update, which will delete locally-stored files that haven't been opened for a set number of days. I am also wondering if those who lost files had Storage Sense turned on prior to the update, and those who did not lose any files had it turned off. Thinking even further, could it be that the update process is turning it on by default with a value for the number of days which is causing the utility to remove files?
I think you're on to something there, BarryG_961!
This helps me with a discrepancy I have noticed in the way the October Update has affected different users. I was looking for a common denominator for those who ACTUALLY LOST data rather than just had it arbitrarily relocated as in my case where I had to find about a terabyte of ostensibly missing data. I found it in C:\users\USERNAME as opposed to C:\users\USERNAME/Documents or any of the variations thereof.
Naturally I was thinking about a common make of computer or even of CPU.
But I uninstalled the OneDrive App when it first came in with Windows 10 back in 2015 and have never missed it. If I want to use OneDrive to store Data I just go to it via Edge.
Certainly if this is TELLING the computer to delete files and folders then that explains a LOT!