Premium lounge closed when every one else is opened

So I'm a gold SA voyager member. Bought my ticket on Ethiopian airlines to a destination, Yaounde, not served by SAA. Boarding is at 2300. I decide to walk all the way to the star alliance premium lounge at OR Thank and find it closed when all the other lounges are opened. There is a lady sitting inside completely ignoring me, reading a newspaper. I decided to go to enjoy the courtesy of another lounge that welcomed me because of my platinum membership on their loyalty program. Will definitely think twice next before buying a star alliance ticket.