I have done a TON of Staples rebates and always send a copy of the shipping doc and a copy of the email order confirmation, along with the original UPC. Never have a problem with them.
Since I started filing the rebates on line, as I did for this scanner and a mouse I ordered at the same time, amd then mailing the docs above after the goods arrive, I usually have the check in about 4 weeks. I also ordered this scanner on the previous $70 MIR deal and it took 4 weeks to the day.