Order Confirmation contains Discount codes used on order.

Was told to use New Signup Discout Coupon #ID. This is already set to zero and the issue is with the EXISTING Customer order confirmation emails, not new signups. For example a long time customer orders a product and the admin uses a special Discount code available only to the site admin. The "secret" coupon code now shows up on the automatic email sent to a customer after the order is processed.

Any help would be good. As of now I'm stuck with changing the numbers of uses to one use per customer and changing it when I need to use a coupon. This is not a long term solution.