I am facing a similar problem to this question has anybody found a solution to it
http://www.telerik.com/community/forums/aspnet-mvc/grid/grid-does-not-filter-when-filterby-major-startswith-mba.aspx#1795473
the sample application here is also not filtering
http://www.telerik.com/community/forums/aspnet-mvc/grid/is-there-a-way-to-save-grid-stage.aspx#1224347
The application you have referred uses hidden fields that are updated through js on DataBound
event of the grid like
$('#currentPage').val(currentPage);
$('#orderBy').val(orderBy);
$('#groupBy').val(groupBy);
$('#filterBy').val(filterBy);
However, if you have a look at keys that grid posts when filtering, it looks like
so, in that application if you are trying to access filtering info in _index method which provides data to grid ajaxically, you have to change parameter name from filterBy to filter like
public ActionResult _Index(string page, string orderBy, string filterBy, string groupBy)