Get nested field of Autoform modifier

I have a schema set up like this…

Schema.ContactDetails = new SimpleSchema({
  orderedBy: {
      type: String,
      label: "Ordered By",
      optional: true,

Orders.attachSchema(new SimpleSchema({
orderDetails: {
      type: Schema.OrderDetails,
      optional: true,
      blackbox: true

I then have an Autoform set up with this…

{{#autoForm collection="Orders" id="updateOrderForm" type="method-update" meteormethod="updateOrder" doc=this}}

And this is the updateOrder method…

updateOrder: function (doc,doc_id) {
    check(doc, Orders.simpleSchema());

    //Modify doc here

    Orders.update({_id: doc_id}, doc); 

The above console.log(doc); outputs the following…

{   '$set': 
    { createdBy: 'o5Wye6LLMGNXLn7HY',
        createdAt: Sat Apr 09 2016 22:15:27 GMT+1000 (AEST),
        'contactDetails.orderedBy': 'MvCun8p6vxndj3cr8',
        updatedAt: Mon Apr 11 2016 11:47:31 GMT+1000 (AEST) },
    { […]

My problem is that I need to get the ‘contactDetails.orderedBy’ value in the updateOrder method but I can’t seem to access it. I have tried the following…

var orderedBy = doc.$set.contactDetails.orderedBy;

Exception while invoking method ‘updateOrder’ TypeError: Cannot read property ‘orderedBy’ of undefined

var orderedBy = doc.$set.‘contactDetails.orderedBy’;

Unexpected token error

Thanks in advance

Answered here…Dynamically access object property using variable

and here…Extract value from object using javascript

var orderedBy = doc.$set['contactDetails.orderedBy'];