Retrieve data from visible false BoundField of Gridview

I have this BoundField in a GridView

<asp:BoundField DataField="ReportId" HeaderText="RId" Visible="false" />

But when I try to get text in that field, it returns empty.

protected void gvwReports_RowCommand(object sender, GridViewCommandEventArgs e)
{
    if (e.CommandName == "ViewSchedule")
    {
        int index = Convert.ToInt32(e.CommandArgument);
        GridViewRow row = gvwReports.Rows[index];
        string s = row.Cells[0].Text;
    }
}

but, it returns a correct value if I change BoundField's .Visible property to true