How can I uninstall AEC plugin?

I’m experiencing issues with Ajax Edit comments that have not been addressed in the specific forum.

Here’s my situation:
The plugin was installed more than a year ago and network activated.
When WP 3.5 update made TinyMCE go wonky, I deactivated a lot of plugins to figure out why. AEC was one of them.

After I activated AEC again, the options for AEC on my Admin panel were missing. I figured that perhaps a complete uninstall and clean re-install would fix the problem.

So I did the following:
Deactivated AEC
Tried to delete AEC, but there was no “Delete” option in my Network plugin panel! (It does not appear in my site panel.)
So I went to delete the directory from the plugin directory, but it was not there.
However, there was an AEC directory under “Uploads.” I deleted it.
I went back to my Network Plugin panel, but AEC still showed up, even after refreshing the browser, etc.
I tried to install AEC nevertheless, but the system said that the plugin was already installed.

So my question is, what causes the system to recognize AEC as installed when it is deactivated and its folder is deleted. (There is no “Uninstall” option.)

What file do I need to modify to tell WP that AEC is not installed?

Please help!