Answer: Not on a Friday!
Just downloaded and ran a Mac program called "Disk Doctor Pro". I never did see "Logos" in the list of things that could be tossed, BUT when I started up Logos a few minutes ago, my entire library (in the Application Support folder) had been trashed. So, I'm spending today downloading and installing and reindexing. Happily, I don't use Logos for sermon development, and I can still use Scrivener to work on Sunday's message.
Note to self: don't do computer maintenance on Friday!