No rebate due to postal office mail loss

I bought my laptop in December and filed out my rebate form and mailed it out on December 28th. 8 weeks later i called to find out about my rebates and they told me that it was postmarked 2-5-2008.If the post office lost it or something, its not me fault, these things happend but they don't want to listen to me. I've called and asked to speak to manager no one calls back.