Hmm, well if it happens again I'll let you know. Otherwise I have no received a single spam message since I installed this addon. Absolutely fantastic. I have to say that I would cry without it. I've seen about 20 reported message notifications today, and it's nice not having to see that stupid spam.
Just a thought, would it be possible to hide the "message reported" notification? That way I can pretend that spam doesn't exist :).