12 hours ago was an update from 1.22.0-insiders to 1.23.0-insiders.... everything was OK.
But now, after one more update ...
Version 1.23.0-insider
Commit 95101bf3f6d00105621cdddb639ea62b95ea2468
Date 2018-04-06T08:49:48.798Z
Shell 1.7.12
Renderer 58.0.3029.110
Node 7.9.0
Architecture x64
Does this issue occur when all extensions are disabled?: Yes/No
... all open editors just disappeared. Instead of them - a "Welcome" page.

Hm.
PS: it really can be because of _laggy frozen downloading error_ of the new updates.
So, the problem is when you try to check updates - clock appears on the gear icon ...

... and it gets frozen. No reaction at all. If you hover cursor - it will say "Update is downloading....".
And that's it. So, the only way to bring it back to life is to restart VS Code by closing it. Maybe it causes the damage of the workspace files. I don't know.
@user3323 sorry we had a hickup that caused us to release a newer version with breaking changes to the UI storage. To recover:
Local Storage folder (see below).vscbak and remove that extension (e.g. file__0.localstorage.vscbak becomes file__0.localstorage (if the files without extension already exist, make sure to delete them first)Location:
Windows: C:\Users\<name>\AppData\Roaming\Code - Insiders/Local Storage
Linux: /home/<name>/.config/Code - Insiders/Local Storage
macOS: /Users/<name>/Library/Application Support/Code - Insiders/Local Storage
@bpasero , thanks for reaction!
Yes, it worked.
And a little remark about renaming process...

... in the case, that new localstorage's files already exist - first you need to delete those.
@user3323 great to hear this recovery worked, I have updated the steps to make sure to delete the existing files first.
Closing, will point other users to this in case we have more.
I saw the same thing in that extension enabled/disabled state was lost. The recovery above fixed it.
Most helpful comment
@user3323 sorry we had a hickup that caused us to release a newer version with breaking changes to the UI storage. To recover:
Local Storagefolder (see below).vscbakand remove that extension (e.g.file__0.localstorage.vscbakbecomesfile__0.localstorage(if the files without extension already exist, make sure to delete them first)Location:
Windows:
C:\Users\<name>\AppData\Roaming\Code - Insiders/Local StorageLinux:
/home/<name>/.config/Code - Insiders/Local StoragemacOS:
/Users/<name>/Library/Application Support/Code - Insiders/Local Storage