I've seen that happen before. Usually, the meeting chair has noticed and taken the offender aside outside the meeting to talk with them.
Even as a newcomer, you can feel free to say "I am feeling concerned and uncomfortable right now about what's happening in this meeting - clearly this gentleman is under the influence and potentially drove here... what can we do to support his safety and our own sobriety?"
I'm sorry that happened to you, it does happen from time to time..... it sounds like that meeting wound up letting the guy and everyone else down by simply turning a blind eye.