Back in January when I bought a Wahl clipper set, I sent away for a $5 mail-in rebate. I took a high-resolution photo of all of my rebate materials first.
A few weeks later, I received a letter stating my purchase didn’t qualify. Hmm. I knew for a fact that it did indeed qualify for the rebate.
I contacted the customer service folks, sent them the photo of my materials, and today I received notification that my rebate was approved.
No matter the price, if you want to make sure you get your rebate, take a photo or scan your receipts/UPC/forms/whatever. People who are really organized might even keep a spreadsheet or a list to keep track of when they submitted their rebate, and when it arrived.