Plugin not showing in installed plugin list

Hi

I have the Google Adsense plugin (by google) installed. I can see it’s menu item in Settings and use it to manage my ads on my site.

However it doesn’t show in the installed plugin list. If go to add the plugin it says it’s already installed (the button says Installed and is greyed out).

Any idea why this might be?

I’m not running multisite, just single site.

Can I run the plugin uninstaller for this plugin to nicely remove it and have it remove itself nicely?

Olly