Alright, well you've forced me to bring my warlock out of retirement for this.
This is the pet summoned by Grimoire of Supremacy and it's treated exactly the same as a normal warlock pet, it can accessed through the unitID "Player-Pet" and it causes a SPELL_SUMMON event so there's no reason why it shouldn't be detectable.
Also you can just head into an instance like RFC when you want to monitor events in peace.