You must have a reference to the usercontrol or know its index in the panel's controls collection at least.
forgotpass ff;
private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
{
panel2.Controls.Clear();
panel2.Visible = true;
ff = new forgotpass();
ff.Show();
panel2.Controls.Add(ff);
}
void HideFF()
{
ff.hide();
}