Visible articles within Hidden Menus will ONLY be displayed with the deault template and default layout regardless of which ones you have set.
I think this may be a bug or an ommisson, either way I don't like it
.:EDIT: a work around for this is to place your article within a VISIBLE category witch in turn is nested within a HIDDEN catergory.
--hidden_category
-----Visible_Category
---------Visible Article