odd problem 99% of files from Documents folder keep deleting themselfs

[Glaucus]

This is second time parents have had this happen.

Neatly all files and folders from document folder disappear and are found in recycle bin. Now I thought it was user error and keyboard mashing. But odd how a couple of folders remain but with only a couple of files in, while other folders are removed totally.
I had set it to sync with one drive as well, but this seems turned off now. And no files or folders are synced and nothing in OneDrive recycle bin.

I've ran several antivirus/malware and found nothing. Running one last online antivirus Trend houseCall almost finished and so far found nothing.

This is windows 8.1, and tbh I'm stumped. I've never had anything like this and I'm not so sure it user error, due to some folders remaining. But files within those folders disappearing. Sits not like an accidental select all and delete.

Any ideas? Any known viruses that do this, or anything else?

Thankfully so far it's just been to restore the recycle bin, so nothings been lost. I told them ages ago to back up to usb as well. But apparently that failed to copy them over.

 

[Raumarik]

Only time I've lost files like that was because of Onedrive (or rather Skydrive at the time). I ended up having to restore from Crashplan because of it. Never quite trusted it since, still no idea WHY it actually happened. It only left folders and files that were in use at the time too.

I had Malwarebytes pro protection on at the time so it's unlikely to have been any malware.