Major Audio System Problem...

I own a 2001 Honda Civic EX
Recently I removed the air box but while doing so my friend had removed the battery wiring.
Knowing this is beyond the point, however, this engages the theft protection in the audio system.
I seem to have lost the card that held my 5-digit code, and now am shitless of the code!
In the book it says to call the dealership, but I'd need my systems serial number
Where might this serial number be located, how might I obtain it?
Any input would help, I've got a long drive this weekend!
Thanks!