msshushu,
I don't think OlegK understands what you're asking for. I've encountered the same issue as you too.
My solution was to generate my own map of field name to column index as part of initialising my grid.
Rough JS psuedocode:
grid = jQuery(“#grid”).jqGrid({colModel:myColModelCallback });
myColModelCallback {
colModel = [{name:'col1'},{name:'col2'}];
global var colModelMapping = {};
colModel.each(function(index,value) {