I am able to add new rows to my WHDG using JavaScript.

var childGrid = _getChildGridView();
childGrid.get_rows().add(newRow);

In my example, if a Parent had 3 Child Rows (1 row was present, the other 2 were added on the client), I am able to see all of my rows on a PostBack including my 2 new rows. However, only one row has data while iterating the rows. 

        Protected Sub getContainerGrid(ByVal gridView As ContainerGrid)
            ' Iterate through rows
            For i As Integer = 0 To gridView.Rows.Count - 1
                If gridView.Rows(i).Items.Count = 28 Then
                    If gridView.Rows(i).Items(12).Value = "Y" Then
                        gridView.Rows(i).CssClass = "someCssClassName"
                    End If
                End If

                ' Recursively call the method for each row
                If gridView.Rows(i).HasRowIslands Then
                    getContainerGrid(gridView.Rows(i).RowIslands(0))
                End If
            Next
        End Sub

Here is the result...

gridView.Rows(0).Items(3).Value = "100.00" (last row added on client)

gridView.Rows(1).Items(3).Value = Nothing (second row added on client)

gridView.Rows(2).Items(3).Value = Nothing (present row on load)

Any help would be appreciated!