After numerous complaints that users were having all their files deleted during upgrading, Microsoft has pulled their Fall 1809 Windows 10 update and recommends to users who have lost files to use Recuva to get them back (but only in some cases). This is a similar issue that plagued their 1803 update last Spring. Another issue is that your profile may get deleted as well! So it's really serious issue and Microsoft was wise to pull it back. But it's baffling that since millions are part of the Windows 10 beta test, how this could happen without Microsoft seeing it coming.