I have been successfully running Unraid for a few years. A week back, on eof my drives went offline and was shown as being emulated. I replaced it with a new drive and the data got rebuilt. To my surprise I noticed all my docker went away. They got automatically downloaded but all the user specific data is gone. i.e. appdata looks like a fresh install. Have I lost my appdata? Why would this happen since the server didn't fail really - one drive failed and Unraid rebuilt the array. So why were my dockers containers reset. Same with VM.

Ideally, appdata would not even be on the array. 

 

Nothing in your description seems to explain what happened so something is missing. 

Maybe Diagnostics would tell more, especially if you haven't rebooted.