JQGrid search functionality works if two same name column interchanges - jqgrid

Question

am using JQGrid and enabled Search to true . everything is working fine.
scenario: there are two budget column one is for footer total and another is for column
$("#BudgetGrid").jqGrid({
datatype: 'local',
data: JSON.parse($('#JsonData').val()),
colModel: [
{
name: 'BudgetId',
hidden: true,
classes: 'budgetid'
},
{
name: 'Month',
hidden: true
},
{
name: 'MonthInWords',
resizable: true,
//align: 'center',
label: 'Month',
ignoreCase: true
},
{
name: 'Budget',
resizable: true,
align: 'center',
label: 'Budget',
ignoreCase: true,
formatter: function (cellvalue, options, rowObject, rowid) {
return '<input type="textbox" class="form-control number" id="budget" value=\"' + rowObject.Budget + '\"></input>';
}
},
{
name: 'Budget',
resizable: true,
label: 'Budget',
ignoreCase: true,
hidden: true,
sorttype: 'number',
summaryType: 'sum',
formatter: 'integer',
formatoptions: {
decimalSeparator: '.', decimalPlaces: 2, suffix: '', thousandsSeparator: ',', prefix: ''
}
}
],
loadonce: true,
pager: "#BudgetGridPager",
viewrecords: true,
ignoreCase: true,
rowNum: 12,
footerrow: true,
userDataOnFooter:true,
gridComplete: function () {
var objRows = $("#BudgetGrid tbody tr");
var objHeader = $("#BudgetGrid tbody tr td");
if (objRows.length > 1) {
var objFirstRowColumns = $(objRows[1]).children("td");
for (i = 0; i < objFirstRowColumns.length; i++) {
$(objFirstRowColumns[i]).css("width", $(objHeader[i]).css("width"));
}
}
}
, loadComplete: function (data) {
var $grid = $('#BudgetGrid');
//debugger;
$grid.jqGrid('footerData', 'set', { MonthInWords: "Total" });
$grid.jqGrid('footerData', 'set', { 'Budget': ($grid.jqGrid('getCol', 'Budget', false, 'sum')).toFixed(3) }, false);
}
});
$("#BudgetGrid").jqGrid('filterToolbar', {
autosearch: true,
stringResult: false,
searchOnEnter: false,
defaultSearch: "cn"
});
when i write hidden budget up search column search wont work
but when i write budget without hidden and next budget hidden , search works fine.
can anyone please say the reason behind it