Gillette Commercial Operations ripoff rebate offer for Oral-B electric toothbrush Boston Massachusetts

Gillette sells an electric toothbrush for $15.49 and states it will return a $10 rebate. It states the following should be mailed:
.The original completed Certificate - which is very tiny and difficult to fill out with dark blue fill in blanks
.The original proof-of-purchase (UPC) - which is not explained, so I sent everything in the package except clear plastic wrapper.
.Symbol from package
.Your original dated sales receipt with store name, product and purchaase price circled

About 1 month later I received a letter stating:
"We regret that we are unable to process your request as received. It did not meet the proof-of-purchase requirements as stated on the order form."
"If you have questions regarding this offer, please visit www.gillette.com/rebatestatus and we will be happy to assist you."

I tried the specified web site. It asked for first letter of first name, first 3 letters of last name, address and zip code. It came back with same 'proof-of-purchase requirement not met'.

No where does it describe what a 'proof-of-purchase' is and where I can find it. I sent everything but the toothbrush.

Now it says "resubmitted requests must be returned within 7 days from receipt of this letter".

John
Camp Verde, Arizona
U.S.A.