I thought that given I could see the emails via the "Find" window that I could creat a filter to transfer the message to an alternate folder where they could be seen. This did not work. I was able to set up a subfolder in another one of my email account folders and transfer SOME of them directly from the "search" window and then read them. Others, when transferred, appeared with no headers, unreadable, and dated "1969".

Are you sure you have selected menu View (or menu button > View) > Folders > All is selected? Also see Switching the folder pane view.

Given the 1969 issue, it could also mean some date headers are lost. Please have a look at this question - you may need to compact, or recreate folders or delete the .msf files.

As for backing up and restoring profile folders, I would recommend copying the folder content (or entire folder) manually instead of using tools.

Does this help?

Deleting the Inbox msf file did the trick! directory rebuilt itself and I can now see all the headers again! Thanks you! Now to decide how to keep this from happening again. This wouldn't have been the first time' I tend to keep ALL emails. There have been a few times where I had to go back into emails years back to find a particular piece of information, and I did this by keeping all emails within one folder. This hasn't been the first time emails have "disappeared" on me!

Glad it worked. if it happens again, you can also try the Repair button located in a folder’s Properties that should do the same. And of course it can be good to check what just happened to the system just prior to when the issue reoccurred.

Normally, compacting folders is a good thing to do but also done automatically in recent Thunderbird versions according to some of its settings. Compacting is just one thing to keep things running. As you can read there, any user is of course free to cope with their mail as they like, but chances of issues occurring may increase according as file sizes increase to name one. Using separate folders can prevent that, and search capabilities in Thunderbird are not limited to one folder. Having one folder sized e.g. 2GB is not unusual today, and perhaps that’s just considered small in 10 years, though Thunderbird and other applications may probably have required some updates in order to cope with larger sizes by then. Antivirus software can be another culprit, and frankly I think most users suffering this issue use them and allow such software to interfere in Thunderbird while doing so can be considered questionable.

If people would see their email inboxes as real postboxes needed to be emptied once in a while instead of an unlimited digital container, they would probably move or even delete messages sooner, moreover because many people use or moved to IMAP nowadays so things keep growing and growing. As the "keep things running" article points out, there are things to keep things healthy and minimize risks, even though a power outage or disk crash could always occur and be devastating, so backing up an entire profile or just copying or moving important or sensitive messages periodically may be good anyhow. And of course there are bugs that may come up...

It’s just some thoughts, hope they help. ;)

Thank you for your time and effort, Tonnes! I have already started compacting and archiving my email!