Not able to fetch scope value in back button method in Ionic

On same template ionic is unable to get the value in ion-nav-bar directive.

Problem - Whatever the amount I filled in textbox <input type="text" placeholder="70" ng-model="getamt"> in below mentioned code, I am able to get the same value at Getting Amt here: {{getamt}} ie.if I type 56 I am able to get 56 typed like Getting Amt here: 56 BUT I am expecting the same to print at Not updating Amt {{getamt}} but in this case I am not getting any value I need to send this value to my previous page…so I am trying to do this stuff.

Let me know how to fix this weird issue with ionic.

  <ion-nav-bar class="bar-stable">
    <ion-nav-back-button class="button-clear" ng-click="myGoBack(getamt)">
      <i class="icon ion-ios7-arrow-back"></i> Not updating Amt {{getamt}}

  <ion-content class="has-subheader" padding-bottom="true">
    <div class="row">
      <div class="col col-30">
        <input type="text" placeholder="70" ng-model="getamt">
      <div class="col col-30 item">
        Getting Amt here:  {{getamt}}

I am not sure, but I believe when ionic converting the directives, may be its not able to save the scope…but its all my guess…let m eknow what I am doing wrong if any or other work around for this.

My controller code -

.controller('mystate2Ctrl', function($scope, $stateParams, $localstorage, $rootScope, $ionicHistory) {
  console.log("----- mystate2Ctrl -----");

  $scope.myGoBack = function(val){

  $rootScope.$on( "$ionicView.leave", function( scopes, states ) {
    if( states.stateName == "app.mystate1" ) {
      console.log("In Ionic View blah blah code here");