Let me get this straight… They deleted their only other copy of the files from their old drives immediately after uploading them to OneDrive? Microsoft has some fault here, but that is also an unbelievably stupid decision on the user’s part. It also sounds like they were planning to copy the files to a single new drive and immediately delete them from OneDrive, which is equally stupid. Are they allergic to having their files in multiple places or something?

It’s an awful situation to be in, but it could’ve been avoided by simply having a second copy of the data, which is pretty much the simplest backup system.