You need to confront your boss about excluding you from the meet

Sometimes, you have to talk to him directly to express your concern about excluding you from the vendor meeting since you are the project lead.  Especially, at this point, he is leaving and you don't have to worry about him.  Going over him to his boss at this point is not wise move since his boss has already agreed to remove him.  You don't want to give your boss' boss an impression that you are the one who will go over your boss to report something.