WP detectors will not be able to detect which theme your website are using. And your theme will not be renamed. The plugin will just hide its name.

The Scan WP Theme and Plugin Detector is a free detector you can use on your own site in the admin area. Detect other sites' themes and plugins.

Scan WP is a free tool you can use on your own site on any page you wish. Engage your users while increasing time on site and reducing bounce rate.