A friend on b.net said that plague (as in plaguing anywhere) could be detected because it is a unit, and could have a location centered on it to remove it and create men where it used to be, just like dark swarms and webs. He also said that he had a editor for it, but he didn't remember the name (which beats me on how he doesn't remember).

So I was wondering if there was an editor to detect a plague cast, or some other way to detect a plague that was cast on nothing.

No, he must be confusing something. Dark swarms can be detected, but not plague.

Alright, thanks.