Bugzilla

The next time you are in trouble, you can easily ask on https://support.mozilla.org/, where people will be more than happy to help.
You can also chat real-time with other users in the Mozilla Matrix channels, see https://wiki.mozilla.org/Matrix.
Or, if you look for third party help, there's a Reddit Firefox group where people are also happy to help.

Usually Firefix doesn't have to notify about upgrades and bookmarks loss, because bookmarks loss is never an expected outcome, it can happen only if the profile gets messed up, or there is some kind of disk/memory corruption. For those cases we provide a minimum of 15 days of bookmark backups in the profile folder, as I pointed out.
I don't know what's the status of MozBackup, being it a third party tool we have no control over it.

Unfortunately, after the fact, we can't do much, any useful info to figure out what happened have likely been overwritten already.
I hope you can use the bookmark backups to restore your bookmarks into a clean profile.

I'll take your feedback about the backup and restore process being hard to find and understand, we already have plans to make the bookmarking experience better, and that will be part of it. Unfortunately I can't give a date for that work yet.

The next time you are in trouble, you can easily ask on https://support.mozilla.org/, where people will be more than happy to help.
You can also chat real-time with other users in the Mozilla Matrix channels, see https://wiki.mozilla.org/Matrix.
Or, if you look for third party help, there's a Reddit Firefox group where people are also happy to help.

Usually Firefox doesn't have to notify about upgrades and bookmarks loss, because bookmarks loss is never an expected outcome, it can happen only if the profile gets messed up, or there is some kind of disk/memory corruption. For those cases we provide a minimum of 15 days of bookmark backups in the profile folder, as I pointed out.
I don't know what's the status of MozBackup, being it a third party tool we have no control over it.

Unfortunately, after the fact, we can't do much, any useful info to figure out what happened have likely been overwritten already.
I hope you can use the bookmark backups to restore your bookmarks into a clean profile.

I'll take your feedback about the backup and restore process being hard to find and understand, we already have plans to make the bookmarking experience better, and that will be part of it. Unfortunately I can't give a date for that work yet.