I too lost access to all my accounts because of a bug/glitch in the Microsoft Authenticator app's recovery system. I had the "Backup to iCloud" option enabled, and I even tested it (backed up & restored a couple of times) before I continued adding accounts to the app. I really trusted the app to keep all my accounts safe.
Then my iPhone's battery died, and after a sequence of stupid events, the Apple Store where I took it to be serviced ended up trashing my device. They gave me a new iPhone and I restored everything from an iTunes backup I had made hours before.
And now I need Microsoft Authenticator to get to all my accounts again -- except it can't find the **bleep** backup in my iCloud account. Someone else in a similar situation posted logs showing that the app itself deleted the backup: https://docs.microsoft.com/en-us/answers/questions/432592/authenticator-restore-on-iphone-failed-backup-dele.html
WTF Microsoft? What do I do now? Trusted the wrong guys, again. Should have gone with Google Authenticator instead like everyone else.