The provided link appears to work for active rebates only. That is when you are still within the qualifying period to make a purchase. I have a few days left to submit my form, but my rebate form was partially destroyed. At least I was able to read the manufacturer's website to locate one there. Try entering your phone model and the word rebate or promotion in a search engine like Google or Bing.
The instructions on the receipts and documents area will leave you frustrated. This forum was my last attempt to locate some worthwhile support, but it was disappointing as well.