Go into your one drive website and go to recycle bin. All of my files were there, yours should hopefully be there too.
I have not attempted to update any of my 4 PCs from 1803 to 1809, and have been making sure I have complete backups in anticipation of the worst. I'm following all the postings about this issue, and it's amazing how you've stumbled upon all your missing files in your online recycle bin! I hope everyone who has been affected tries that with the same success. It would be pretty incredible if Robert Ziko's 220 GB of missing files wound up there. I mean, how long must it have taken to upload all that data to the cloud?