Disc replaced - Now Docker images have disappeared

[philw]

I setup my server four years ago, and a lot of the config choices I made back then were probably not the best, but the server has been ticking along nicely ever since.
I recently had a disc failure - I went through the replacement procedure, and restored it, or so I had thought from parity etc.
Again, I left it to its own devices.
A couple of months passed.
Yesterday I noticed that one of my discs, I assumed the replacement, was disabled, although I could find no explanation as to why.
SMART results seemed OK.
I restarted the server and then saw an option to add the disc back, which I selected and the dashboard showed it checking against parity.
Hours later the disc is now enabled, and scanning around my various folders, everything appears to be intact. At least I think everything still OK.

But - all my carefully setup Docker images have disappeared, not appearing in the Dashboard. I dread having to re-configure all of those.

/mnt/user/system/docker.img is still there, and /mnt/cache/appdata shows folders for each of the images I used to have still.

Before I start reinstalling docker images (and I am hoping that they see the original configs in /mnt/cache/appdata), I would like to understand what has happened.

Q. Why was the disc disabled?
Q. Should I have NOT added it back?
Q. Did adding it back somehow trash the Docker images?
Q. Is there anything to be done to get them back other than re-installs?

I have disabled parity checking for the time being while I figure out what has happened - I am minded to attach an external USB drive, and backup anything irreplaceable, before proceeding with anything.

[itimpi]

If you have not rebooted then you are likely to get better informed feedback if you attach your system’s diagnostics zip file to your next post in this thread that cover the actions you took so we can get an idea of what happened under the covers.

[philw]

It has been rebooted unfortunately. 
I can now see files on that disk not on others, and it appears? to all be intact, just no Dockers,
If I reinstall Docker images, as part of that reinstall will they each see the original configs that remain in /mnt/cache/appdata?