how to delete an order that has already been sent and received?

I received an order on 7th Oct and posted it. The buyer received it on 14th Oct and has confirmed she did and that she did not place the order again. This order has now (15th Oct) appeared back in my current orders section telling me to send now. I don't want to delete this incase it looks dodgy on the customers end.  Is this a known system error? 

View Entire Topic

Friday is maintenance day and there are often glitches. Maybe it is just a glitch.