How to find out who is using your plugin

Is there a way to find out who is currently using your plugin? I just want to see how it renders amongst different themes. I tested my plugin on a bunch of themes/browsers/devices prior to releasing, but realized that on a particular theme, it doesn’t render correctly. This was brought to my attention by somebody who currently has my plugin installed.

I tried a few ‘source code search engines’ to see if would return results for some of my plugin specific names, but had no luck.

Thanks