Navbar and nested views - back button not showing up

ionic-v1
1

Ok my html:

<body ng-app="starter">
 <ion-side-menus>
  <ion-pane ion-side-menu-content>
    <ion-nav-bar class="bar nav-title-slide-ios7">
      <ion-nav-back-button class="button-clear">
      <i class="icon ion-ios7-arrow-back"></i>
      Back
      </ion-nav-back-button>
      <ion-nav-buttons side="right">
   <button menu-toggle="right" class="button button-clear button-assertive button-icon icon ion-navicon "></button>
  </ion-nav-buttons>
    </ion-nav-bar>
    <!--main app view-->
    <ion-nav-view animation="slide-left-right"></ion-nav-view>

  </ion-pane>
  <ion-side-menu side="right">
    <header class="bar bar-header bar-dark">
      <h1 class="title">Menu</h1>
    </header>
    <ion-content class="has-header dark-bg">
        <ion-item nav-clear menu-close href="#/">
          Home
        </ion-item>
        <ion-item nav-clear menu-close href="#/hey">
          Hey
        </ion-item>
      <ion-list>
        <ion-item nav-clear menu-close ng-click="login()">
          Login
        </ion-item>
        <ion-item nav-clear menu-close href="#/app/search">
          Signup
        </ion-item>
      </ion-list>
    </ion-content>
  </ion-side-menu>
</ion-side-menus>


</body>

then my simple angular:

.config(function($stateProvider, $urlRouterProvider) {
  $stateProvider
  .state('app', {
    url: '/',
    templateUrl: 'views/home/index.html'
  })
  .state('hey', {
    url: '/hey',
    templateUrl: 'views/hey/index.html'
  })
  $urlRouterProvider.otherwise("/");

});

views content (views/home/index.html)

    <ion-view title="Home" hide-back-button="true">
<ion-content class="padding">
<div class="content padding">
<div class=" text-center">{{config}}</div>
<button class="button button-block button-outline button-calm">Login</button>
<button class="button  button-block button-outline button-positive">Login</button>
</div>

</ion-content>
</ion-view>

views content (views/hey/index.html)

    <ion-view title="#antani">
<ion-content class="padding">
<div class="content padding">
<div class=" text-center">{{config}}</div> damn
</div>

</ion-content>
</ion-view>

why when im on /hey page the back button doesn’t comes up?