Referenced document does not get shown while making populate query

items.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var ItemSchema = new Schema({
    no_of_times_ordered:Number,
    item_name:String,
    item_tag:String,
    item_category:String,
    item_illustrations:[String],
    item_stock:Number,   //0 available 1 last 5 items 2 not available
    item_quantity_ordered:{type:Number,default:0},
    item_price:Number,
    item_img:String,
    no_of_likes:{type:Number,default:0}
},{ versionKey: false });

module.exports = mongoose.model('items',ItemSchema);

foodtruck.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var Items = require('./items.js');


var FoodTruckSchema = new Schema({
    foodtruck_name:String,
    foodtruck_location:String,
    foodtruck_rating:{type:Number,default:5},
    foodtruck_total_votes:{type:Number,default:0},
    foodtruck_shutdown:{type:Boolean,default:true},  // true closed   false open
    foodtruck_tag:String,
    foodtruck_open_status:{type:Number,default:1},   //0 open 1 closed
    foodtruck_starting_timing:String,
    foodtruck_closing_timing:String,
    foodtruck_cusine:String,
    foodtruck_img:String,
    foodtruck_logo:String,
    item_list: [ {type : mongoose.Schema.ObjectId, ref : 'items'}]
},{ versionKey: false });



module.exports = mongoose.model('foodtruck',FoodTruckSchema);

The query to add item is as shown below:

var addItem = function(req, res) {
    var foodtruck_id = req.body.foodtruck_id;
    var newItem = new item();
    var itemList = [];
    newItem.item_name = req.body.item_name;
    newItem.item_tag = req.body.item_tag;
    newItem.item_category = req.body.item_category;

    for (var key in req.body) {
        if (req.body.hasOwnProperty(key)) {
            if (key == 'item_illustrations') {
                newItem.item_illustrations = req.body[key];
            }
        }
    }
    newItem.item_stock = req.body.item_status;
    newItem.item_price = req.body.item_price;

    if ((foodtruck_id) && (foodtruck_id.trim() != '')) {
        foodtruck.findById(foodtruck_id.trim(), function(err, foodtrucks) {
            if (err)
                res.json({
                    status: '500',
                    message: 'There is no data available'
                });

            newItem.save(function(err, savedItem) {
                if (!err) {
                    foodtrucks.item_list.push(savedItem._id);
                    foodtrucks.save(); 
                    console.log(foodtrucks);
                    foodtruck.find({
                        _id: foodtruck_id.trim()
                    }).populate('item_list').exec(function(err, foodtrucks) {
                        res.json({
                            status: '200',
                            message: 'New item added successfully',
                            data: foodtrucks
                        });
                    });
                } else {
                    res.json({
                        status: '500',
                        message: 'Error while saving new item'
                    });
                }
            });


        });

    }

}

Now here, what I am doing is , I am creating a new item and updating the reference of newly added item to foodtruck accordingly. Everything works fine and item is created, its _id is pushed to foodtruck.item_list. Now If I put simple find query(without populate ) the query shows the reference of newly added item.

But when I use populate query to extract the reference item, it does not show the last added item. Is it like, populate query works in different way or how can I improve this query?

via M thaker