It's happened, you just don't hear about them.
Maybe I don't understand anti-terrorism... but why trot out these phony stings and make the public think that these are just a bunch of incompetent over-hyped organizations (and I mean terrorist and intelligence alike)? If we are supposed to be suspicious and wary, wouldn't it be beneficial to have something really scary to feed the public?
But I've said all I'm going to say on that.
Business plan of every major religion.