js/libs/ember-data.js
function addUnsavedRecords(record, key, data) {
  if(record) {
    data.pushObjects(record.get(key).filterBy('isNew'));
  }
}
function addUnsavedRecords(record, key, data) {
  if(record) {
    data.pushObjects(record.get(key).filterBy('isNew'));
  }
}
If there are any unsaved records that are in a hasMany they won't be in the payload, so add them back in manually.