js/libs/ember-data.js
function(type, id) {
    type = this.modelFor(type);

    id = coerceId(id);

    var record = this.typeMapFor(type).idToRecord[id];

    if (!record) {
      record = this.buildRecord(type, id);
    }

    return record;
  }
function(type, id) {
    type = this.modelFor(type);

    id = coerceId(id);

    var record = this.typeMapFor(type).idToRecord[id];

    if (!record) {
      record = this.buildRecord(type, id);
    }

    return record;
  }
Returns id record for a given type and ID. If one isn't already loaded,
it builds a new record and leaves it in the `empty` state.

@method recordForId
@private
@param {String or subclass of DS.Model} type
@param {String|Integer} id
@returns {DS.Model} record