Hmmm ... replying to own posting, but just thought of a question.
Obviously, you are remotely hosted. Does your hosting plan have any tool that, when setting up a domain and choosing an app to run in it, associates a DB with the domain?
The one file that is named the same for both packages is index.php. Opening them with a text editor will tell you which they belong to. Word Press index.php has this comment:
* Front to the WordPress application. This file doesn't do anything, but loads
* wp-blog-header.php which does and tells WordPress to load the theme.
*
* @package WordPress
*/
Moodle's index.php has a copyright notice that's obviously Moodle.
The reason I ask the question: version of Word Press am using has a config file but it's named wp-config.php. The default for your domain, if one points to a index.php file, should be to the one for Moodle - unless that's been replaced. If it had been replaced one would not be getting that DB error page served from Moodle (I would think).
And, the error page indicates that config.php might be pointed to a different DB using a different DB User/Password. That's why I asked the question.
One last ... probably should have been first ... does your provider have a recent backup of your files for that domain? The 'easy button' here might be asking them to restore the file(s).
'spirit of sharing', Ken