Mysteriously redeemed gift certificate

I've got a puzzle. Someone emailed a gift certificate quite some time ago and the customer has been quite slow asking for help, with an odd phone call or email every few months. I lost a chunk of emails so I can't figure out part of what happened but the latest is when she tries to redeem, it comes back as "Invalid Coupon Code". I checked her code and it says it was redeemed on 10/8 and gives the customer number. I seem to remember at one point just giving up and redeeming the code on behalf of a customer but I don't know if this is that case since that date is where I'm missing a huge chunk of emails. The customer in question is indeed a bogus one that I created, but the order in question was also bogus. It was an order I did to get a product linked in the "customers also bought" field before I had the cross-sell installed. :oops: But the thing is, there was no gift certificate used in that order! So I deleted the order to see if the gift certificate would automagically go back, but it didn't. I checked the IP address where the coupon was redeemed and while it is not my current IP address, it is my cable company and close enough to my location; same town I get for my current IP. So perhaps I can go ahead and issue another gift certificate to this customer but this just gives me an uneasy feeling; why could I not track down this gift certificate. I am on patched 1.3.7. I should have a backup of my database kicking around with that order not deleted if that would help in debugging this.