In the default, they show at the top of any forum when pinned, but not separated into their own box as mentioned. When you say "at the top of the page" could you explain what you mean? I ask as you mention you cannot see them until the subforum is open. That is correct as you cannot see any topic until you open the forum they are in. However thats with the exception of when viewing the site as a feed on the front end.
Also, depending on your aim, you may be able to use a block. For example, I have seen on some sites, pinned topics have been put in a block on their sidebar using the topic feed.
We cannot comment on the specific theme you are referring to there. For that you would need to contact the author