Model is undefined after transitioning away then back to a route

Question

I have a route.

import Ember from 'ember';

export default Ember.Route.extend({
    model : function (params) {
        return Ember.RSVP.hash({
            eventTypes : this.store.find('event-type'),
            game : this.store.find('game', params.game_id)
        });
    },

    setupController : function (controller, model) {
        controller.set('game', model.game);
        controller.set('eventTypes', model.eventTypes);
    }
});

When I first visit this route all is well. The models get loaded and I can access game and eventTypes from my template. If I am to transition away from this route and then revisit the route both eventTypes and game are undefined. Why would the route transition with out error and return undefined models?