windows invisible when there should have been a lock screen

[themusicgod1]

Shortly after upgrading to focal (a few days) I left my computer alone and went and away for a good long while, long enough for the screen to lock

Came back and
1) the screen was not locked,
2) the dock at the right hand side was still available and i could manipulate it (ie click on the applications that were running, see the screenshots of them when i mouse'd over them)
2) no windows could be seen.

I managed to for example click on the running bitcoin icon in the top right hand corner, those were clickable too, but nothing did seemed to get the windows back.
Alt-tab...
alt-crl up...
super-tab...
nothing i could think of

Wound up exiting out to terminal (ctrl-alt-f3, logging in) killing gnome-shell and they all came back shortly there after.

ubuntu: focal 20.04 lts
gnome-shell:
  Installed: 3.36.1-5ubuntu1
  Candidate: 3.36.1-5ubuntu1
  Version table:
 *** 3.36.1-5ubuntu1 500
        500 http://mirrors.layeronline.com/ubuntu focal/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-shell 3.36.1-5ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-26.30-lowlatency 5.4.30
Uname: Linux 5.4.0-26-lowlatency x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Sat May 2 03:16:38 2020
DisplayManager: gdm3
InstallationDate: Installed on 2017-04-18 (1109 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
RelatedPackageVersions: mutter-common 3.36.1-3ubuntu3
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to focal on 2020-04-25 (6 days ago)

[Daniel van Vugt (vanvugt)]

This is a strange one. Not quite like anything I've seen reported before. If and when it happens again please attach a photo/screenshot of the issue.

When it happens again please also try pressing: Super+D

[Launchpad Janitor (janitor)]

[Expired for gnome-shell (Ubuntu) because there has been no activity for 60 days.]