Calling function outside of stage scope

So that it will be easy for me to call a hideNav() function, I put the function outside the stage scope. You can see the end of the stage closure below followed by the various things I've tried that do not work. Suggestions welcomed. The alert fires fine so it's an issue with addressing the back button on the main timeline.

     .... stage script stuff here

  })("stage");

   //Edge symbol end:'stage'

// If you don't understand a concept, put all the words you know in random order and see if something happens  - but it doesn't

  function hideNav(){

    alert("hide");

    sym.getComposition().getStage().getSymbol("back").hide();

    sym.getComposition().getStage().$("back").hide();

    sym.$("stage").backButton.hide();

    sym.getSymbol("back").hide();

    sym.getParentSymbol().getSymbol("back").hide();

    backButton.hide();

    sym.$("back").hide();

}

PS, yes I tried them one at a time. This is just a compilation of my greatest non-hits.