Have you contacted your host? They might be able to retrieve a backup for you.

Sounds like your server has been hacked, does anyone else know the server passwords?

Thank you! I am working with host now. I can see my files in their file manager, I believe, and I'm asking them about uploading them again.
About a year ago, I defaulted to a "shared" IP address. It didn't seem to be an issue, as my site is a very small-time teacher site. Today at Hostmonster support the gentleman sold me a static or dedicated IP address (I thought I started out that way years ago). Perhaps the shared situation led to this problem.
Thank you for your suggestion!

I finally called Hostmonster and spoke with a live person (after Live Chat and filing a trouble ticket were not successful). The issue turned out to be NOT a database problem, but some kind of conflict with the index files between Concrete5 and my Wordpress blog. I haven't touched a thing on the website for several months, but somewhere something got crossed. This type of crisis has happened a few times over the years. Fortunately, whenever I've called Hostmonster they have resolved the problem.
Now I'm going to try to log into my site to edit using Concrete5.
Thank you for reading!