mongoose schema reference returning undefined - node.js

Question

I'm just trying to reference accountSchema from productSchema and I'm receiving an undefined result. I think I've referenced 'Account' correctly and that I'm properly creating and saving products. My understanding is that the account field should populate itself with the appropriate account objectId just from being referenced in the model.
//acount.model.js
const accountSchema = new Schema({
email: { type: String, unique: true, required: true },
passwordHash: { type: String, required: true },
title: { type: String, required: true },
firstName: { type: String, required: true },
lastName: { type: String, required: true },
acceptTerms: Boolean,
role: { type: String, required: true },
verificationToken: String,
verified: Date,
resetToken: {
token: String,
expires: Date
},
passwordReset: Date,
created: { type: Date, default: Date.now },
updated: Date
});
module.exports = mongoose.model('Account', accountSchema);
//product.model.js
const productSchema = new Schema({
title: { type: String, trim: true, required: true },
description: { type: String, trim: true, required: true },
category: { type: String, trim: true},
subCategory: { type: String, trim: true },
quantity: { type: Number, trim: true },
price: { type: Number, trim: true },
created: { type: Date, default: Date.now },
updated: Date,
account: { type: Schema.Types.ObjectId, ref: 'Account' }
});
module.exports = mongoose.model('Product', productSchema);
//products.controller.js
//routes
router.post('/', authorize([Role.Admin, Role.Vendor]), createSchema, create);
function createSchema(req, res, next) {
const schema = Joi.object({
title: Joi.string().required(),
description: Joi.string().required(),
category: Joi.string(),
subCategory: Joi.string(),
quantity: Joi.number(),
price: Joi.number()
});
validateRequest(req, next, schema);
}
function create(req, res, next) {
productService.create(req.body)
.then(product => res.json(product))
.catch(next);
}
//product.service.js
async function create(params) {
const product = new db.Product(params);
// save account
await product.save();
// res.json(product);
console.log(basicDetails(product));
return basicDetails(product);
}
function basicDetails(product) {
const { id, title, description, category, subCategory, quantity, price, account } = product;
return { id, title, description, category, subCategory, quantity, price, account };
}
//console.log output of basicDetails(product)
{
id: '600614014d927f29a0fbb162',
title: 'delete from mcjaggerrrrrrrr6789',
description: 'testing delete from role.vendor mcjaggerrrrrrrrrr',
category: undefined,
subCategory: undefined,
quantity: undefined,
price: undefined,
account: undefined
}
category, subCat, quant, and price are all undefined because I didn't input values for them but account is undefined and I'm not sure why. Any help is appreciated!