We bought the three interactive pins Friday at the Sorcerer's Hat Shop and said "OK, now where are our three free pins," but they said they were out, so we said we'd come back Monday. They told us to bring: 1 - receipt from Sorcerer's Hat Shop (to prove we bought 3 pins there) and 2 - certificate. We came back Monday and still no pins, so we showed them the proof and they gave us a different kind of receipt where we filled in our address and they filled in the "3 pins" and told us to watch our mail in about 6 weeks, but gladly, it only took 4 weeks.
I did not save the envelope w/return address, but I did notice that they were delivered from WDW Merchandising, whose phone # is (407)363-6200 and fax # (407)352-6369. Maybe you can call them and arrange to fax the proof.
It seems like the Sorcerer's Hat Shop was out of these pins quite early and did not implement this "ordering" process right away, so sadly many may have missed out. I hope this info helps and you get your pins...they are quite cute.