Im sure im missing something simple here.

this is my code, but no sort shows up when tapping the headers

Code:
var store = Ext.StoreMgr.get('ReferrerJsonStore');
store.on('load', function(){
    var panel = Ext.create('Ext.Panel', {
        title : 'Top Referrers',
        baseCls: 'p-admin-gridview-panel',
        top:20,
        right:20,
        bottom:20,
        left:20,


        layout     : {
            type : 'fit'
        },


        items      : Ext.create('Ext.ux.touch.grid.View', {
            flex     : 1,
            store    : store,
            calcWidth : true,
            features : [
            {
                ftype    : 'Ext.ux.touch.grid.feature.Sorter',
                launchFn : 'initialize'
            }
            ],
            columns : [{
                header    : 'Full Name',
                dataIndex : 'FullName',
                style     : 'padding-left: 1em;',
                width     : '20%',
                sortable  : true,
                filter    : { type : 'string' }
            },
            {
                header    : 'Phone#',
                dataIndex : 'ContactNumber',
                style     : 'padding-left: 1em;',
                width     : '15%',
                sortable  : false,
                filter    : { type : 'string' }
            },
     .
.
.
thanks in advance