I took a walk around the property and unfortunately couldn't find the mill; which I presume means that it was really really old and either fell apart or was replaced by one of the other buildings. I searched for information about the property but could find nothing much, except for references to Stellenbosch University's Oude Molen men's fraternity.
If you do know anything more about Oude Molen in Stellenbosch, please do leave a comment on this post.