The donation ID and the wiki article about making donations with paypal needs to be updated as it is no longer accurate to the paypal site.
http://www.wowinterface.com/forums/f...=donations_dev
They are no longer doing the IDs as they used to, and buttons are not stored in any way (that I could see at least).
Maybe just using the paypal email would be the easiest solution, but that is entirely up to you.