Where would I find where an .htaccess file is located and being used on a Mac OS X Lion server that sets Basic Auth on an Apache server?
You might try looking in /etc/apache2/sites/
That was the directory in 10.6; in 10.5, it was /etc/httpd/sites

On 10.5 and 10.6 server, the server app can be used to set access restrictions, and that is the location where the config files are written.

If your web setup is not complicated, the filename may be similar to 0000_any_8080_(HOST).conf