This seems to be an old thread but I have been searching for the same thing for v2.7. On the user > accounts > audience screen it's missing a couple of audiences for us and found that they're on category context. I then look into the my report - audience report but unable to filter out on those that are on category context. The only way I could figure out is either i) download two report and do a cross mapping and find out the audiences that is not in the system:available audience page, or ii) go to click the category one by one and find out the audiences from there.

It will be really great if there is a column/filter on the audience report that allows us to see from one page on all the audiences that was created, and how they are used......