I just re-read the rebate form that I printed out on 1/5/2001 (IE5 dated the bottom when I printed it, and it printed the URL of the page too) and it too says nothing about participating retailers. They obviously changed the form since then.
It's their tough luck if they try to reneg on this rebate. I bought the drive on the condition that I would get a rebate for the retail box, I met all the requirements in force at the time of my purchase, as specified on the rebate form.
I consider this a contract and I'm holding them to it. I'll take a complaint to my state attorney general's office if need be.