How exactly do you search? There are different ways.

I searched using the little search box in the upper right hand corner of the Thunderbird screen.

I've attached a screen shot of my results.

So we're talking about Global Search. https://support.mozilla.org/en-US/kb/global-search

You can try to rebuild the global database. https://support.mozilla.org/en-US/kb/rebuilding-global-database

I deleted the file and it did not work. The data base did not get rebuilt. There is no global-messages-db file.

Make sure Global Search is turned on. https://support.mozilla.org/en-US/kb/configuration-options-search

It is, and was turned on, still no change.

At the top right of the Thunderbird window, click the menu button , then select Help > Troubleshooting Information > Profile Folder -> Open Folder. This will open your profile in Windows Explorer.

Post a screenshot of the files of your profile with global-messages-db visible, or the part where it's supposed to be. http://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

Here's the screenshot.

Before I read your entire post, I restored global-messages-db from the recycle bin to find out where it was located. Then I deleted it.

This time, when I opened Thunderbird, the database was rebuilt.

It looks like search is working again . . . .

Thanks for your help!