Mongoose Model ObjectId References Not Working - node.js

Question

I'm working with Mongoose models and references. I've been using the code from mongoose's website where it talks about the populate method and references. I am trying to have it save the respective "referenced" ids in both models. It is only saving the reference ids in the story model. Here is the code:
Update: Added schemas at the top to help:
var personSchema = Schema({
_id: Schema.Types.ObjectId,
name: String,
age: Number,
stories: [{ type: Schema.Types.ObjectId, ref: 'Story' }]
});
var storySchema = Schema({
author: { type: Schema.Types.ObjectId, ref: 'Person' },
title: String,
fans: [{ type: Schema.Types.ObjectId, ref: 'Person' }]
});
var Story = mongoose.model('Story', storySchema);
var Person = mongoose.model('Person', personSchema);
(end of schemas)
var author = new Person({
_id: new mongoose.Types.ObjectId(),
name: 'Ian Fleming',
age: 50
});
author.save(function (err) {
if (err) return handleError(err);
var story1 = new Story({
title: 'Casino Royale',
author: author._id // assign the _id from the person
});
story1.save(function (err) {
if (err) return handleError(err);
// thats it!
});
});
When you run this code, it generates this in mongo:
db.people.find()
{ "_id" : ObjectId("5be0a37f1dd61a343115e2c8"), "stories" : [ ], "name" : "Ian Fleming", "age" : 50, "__v" : 0 }
db.stories.find()
{ "_id" : ObjectId("5be0a37f1dd61a343115e2c9"), "title" : "Casino Royale", "author" : ObjectId("5be0a37f1dd61a343115e2c8"), "__v" : 0 }
It appears to not be storing any ids in the people collection within "stories." Wouldn't you want to save the stories ids in the people collection as well?
I tried to modify the code to make it work with (moved the author save function, until after the story id is set):
var author = new Person({
_id: new mongoose.Types.ObjectId(),
name: 'Ian Fleming',
age: 50
});
var story1 = new Story({
_id: new mongoose.Types.ObjectId(),
title: 'Casino Royale',
author: author._id // assign the _id from the person
});
author.stories = story1._id;
author.save(function (err) {
if (err) return handleError(err);
story1.save(function (err) {
if (err) return handleError(err);
// thats it!
});
This gives me an author undefined.

Answer 1

Mongo wouldn't automatically add to the Person "stories" field just because you added a Story object.
You don't really need to store the story ids in Person objects anyway, as you can always get a list of stories by an author with
db.stories.find({author: <id>})
Storing in both places would create redundant information and you'd have to pick one to be the truth in the case of a mismatch. Better to not duplicate, methinks.
UPDATE:
References appear to help you populate referenced fields in queries automatically. According to this post you can retrieve an author and their stories like this:
db.persons.find({_id: <id>}).populate('stories')
Haven't personally used this but it looks pretty handy.
Mongoose docs for populate: https://mongoosejs.com/docs/populate.html