Reader Doug Eddy’s Mail has become forgetful. He writes:
The Find function in my copy of Apple’s Mail no longer works. It will find nothing—not even my name. How can I restore it?
Sounds like the index for your messages is mucked up. I’d try a stern reindexing. And when I say stern, that can mean but one thing: Terminal.
Launch Terminal and enter:
Terminal will work its magic and eventually show you the prompt. When it does, Mail’s index of messages should be back in the pink and searchable.