It's amazing that questions in this forum barely get any answers. Here it goes:
In AkAudioDevice there are two functions for this.
IsPlayingIDActive and IsEventIDActive. The first takes two arguments (Audio Event's shortID and playingID) the second just takes the Audio Event's shortID.
I don't understand the difference completely, I got to this page looking for an answer perhaps you'll be able to help me out as well. Perhaps since Event's have multiple medias, the playingID is associated to a specific media and not just the event itself.