Your suggestion alone did not fix my problem, i needed to use it in conjunction with the following
I needed to make sure that when the search returned no data (null), that i set the drid to have empty datasources, as previously i was only setting datasources if i had data
radGrid.MasterTableView.DataSource = new Object[0];
((GridTableView)radGrid.MasterTableView.DetailTables[0]).DataSource = new Object[0];