Mongo: Nested object array value won't update

I am trying to update the floor_num value from 1 to 9000 in an object in a nested array, in Mongoose:

thingSchema.findById(thingID, function(err, lm) {
  if (!lm){
    console.log(err);
  }
  else {

    if (lm.style.maps.localMapArray){
      for (var i = 0; i < lm.style.maps.localMapArray.length; i++) { 

          if (lm.style.maps.localMapArray[i].map_marker_viewID == req.body.map_marker_viewID) {

              lm.style.maps.localMapArray[i].floor_num = 9000;

              lm.save(function(err, landmark) {
                  if (err){
                      console.log('error');
                  }
                  else {
                      console.log('saved map updates');
                  }
              });
          }
      }
    }
}); 

But the data isn't being updated and there's no error being returned from Mongo