You can see most of what happened here: https://www.twitch.tv/videos/333953560
I quit the game due to the bard bug of not being able to hit my notes. Restarting the client helped in the past for a short while and I was going to try again. After closing and reopening the client it started to patch for a split second and then vanished. Attempting to find the launcher again and it was missing from the Reborn folder. Attempting to reextract files from the zip file was met with errors. The only way I was able to resolve the issue was to delete the containing file and recreate it with a different name so the file path would be different and then reextract the game files to this new location.
All of this is shown in the Twitch highlight.