FindControl Not Working On GridView When Inserting Bound Columns

I have a gridview with several ItemTemplates. The first contains a checkbox the rest contain textboxes. I then added dynamically some bound controls like this:

BoundField bdfPrivName = new BoundField();
clsUtilities.SetBoundFieldCenter(ref bdfPrivName, "PrivName", "Priv Name");
BoundField bdfDescription = new BoundField();
clsUtilities.SetBoundFieldLeft(ref bdfDescription, "PrivDesc", "Description");
BoundField bdfLive = new BoundField();
clsUtilities.SetBoundFieldCenter(ref bdfLive, "Live","Active?");
grdExisting.Columns.Add(bdfPrivName);
grdExisting.Columns.Add(bdfDescription);
grdExisting.Columns.Add(bdfLive);

I then use FindControl() to locate the checkbox and textboxes and perform my logic based the result
foreach (GridViewRow gvr in grdMissing.Rows) {
mckbAny = (CheckBox)gvr.FindControl("ckbAdd");
mtxtApplyDate = (TextBox)gvr.FindControl("txtAddApplyDate");
mtxtDateToAdd = (TextBox)gvr.FindControl("txtAddDateToAdd");
mtxtDateToRemove = (TextBox)gvr.FindControl("txtAddDateToRemove");
}
etc.

This all worked fine. I then got a request to put the bound fields as the second, third and fourth columns, after the check box and before the textboxes. I found that this was easy to do by changing the Add's to Inserts as follows:
grdExisting.Columns.Insert(1, bdfPrivName);
grdExisting.Columns.Insert(2, bdfDescription);
grdExisting.Columns.Insert(3, bdfLive);
It looked fine of the page, but the FindControl(), all of them fail to work.