code: function(theirItem) {
          var count = this.world.getItemCount();
          var item;
          for (var i = 0; i < count; i++) {
              item = this.world.getItemAt(i);
              if (item._originalForNavigator === theirItem) {
                  return item;
              }
          }
  
          return null;
      }
docs: private