Any hits you get when you search with Thunderbird will tell you what folder they are in, though you may have to right-click on the column header to show the "Account" and "Location" columns. I bet they are still buried somewhere in your Inbox.

It could be you are using Threaded View, which groups multiple emails into one "conversation", which can be confusing sometimes. Here's an article about Threading and how to use, enable, and disable the feature:

https://support.mozilla.org/en-US/kb/message-threading-thunderbird

Thanks for the prompt reply.

I checked and no it is not in "threaded view."

Tom

I should have clarified - the "Search" I was talking about above is the Global Search feature, which will search all accounts and folders.

The Quick Filters feature searches only the current folder, so if use it while viewing the Inbox, and Quick Filter finds them, they can only be there.

There's a "pin" icon to the left of the Quick Filter box that makes it so filters used on other folders will persist when you change folders. Could that be enabled?

Can you find the "missing" messages when you sort the folder list by the known Recipient or Correspondents or Subject?

Sorry no. When I search with the quick filter it finds the recipient and can find the emails. But the emails do not appear in the inbox or any other folder. The "pin" icon has no effect on this search. It almost appears that the emails I am looking for are in a "hidden" folder??? or hidden by some sort of filter in the inbox. How do i turn that "filter" off?

Maybe the folder index is corrupt or out-of-sync. Try repairing the folder in question. Right-click on the folder name, choose Properties, General Information tab, then click the Repair Folder button.

Thanks that seems to have solved the problem.