My mother-in-law taught me a neat trick that works, on mail-in rebates: send it with delivery confirmation. It costs extra, so it is only worthwhile if your rebate is large enough to cover the cost, and then some. We bought a computer, nine years ago, with $385 in rebates: sent them with delivery confirmation, received our rebates. Have done it with smaller rebates, always get them. Have sent in a few without delivery confirmation, never received them. Something to consider. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII