Software Registration Question

I sold one of my Jam Packs today. The person I sold the Jam Pack to wants to register the Jam Pack. I do not have the serial number. I threw out the box a couple years ago. I went to www.apple.com/register to logon and see all of the apple software I have registered. It does not allow me to see that. How and where can I see what the serial number of the legal software that I registered with is?

 

Yes, I threw the box away. I didn't even think about the serial number on it. I registered it once a couple years ago and that was it. Each time I installed it I just bypassed the registering it again. Now I am at a loss. The buyer of the software wants to transfer the registration over to her. If I cannot get the serial number she wants to return the software back to me. Which is fine, she has that right. You would thin that by logging into the registration site I could retrieve my serial numbers that I registered.