If there is a full server it is hard for people to see everything that is going on. Sometimes we dont look at the chat because there is other things that are more important especially if he was the only one on the server.
You could of contacted him through @ if it was important and im sure he would of answered you. Just because he didnt reply to your message in chat does not mean that he shouldnt be an admin because in fact thats what he is.
If it was really important im sure you could of tried adding him on steam and he could of helped you there. You might just need to wait a little bit im sure he would of helped you.