Sleep Train & Serta Matress Defective Mattress & Warranty Not Honored San Diego California

I purchase a $2000 Cal King mattress on Sleep Train's exchange program to save about $300.  I was informed by the sales man the mattress was delivered to a previous customer and was in their possession for 5 days.  I was assured that the Serta warranty would be honored if anything was wrong with it.  I was told the mattress was inspected and in new condition.

The mattress was delivered and looked new but had a nasty smell.  The delivery guys told me it would go away in a couple hours and the smell was due to the mattress being treated with a disinfectant and wrapped in plastic immediately afterward.  After the first night I noticed there were two very noticable sags located were two people would normally sleep, separated by a raised bulge.

I called Sleep Train and they basically threw up there hands and said it was not their problem.   I was instructed to call customer service who said it was a warranty issue.  Customer service sent me an email with a description of how to file a warranty with Serta.  Bottom line, the mattress does not meet Serta's bogus warranty requirements and I'm stuck with a smelly lumpy mattress that's in worse shape than the one I had them hall away.

The warranty test is bogus because it requires a first straight edge to be suspended horizontally across the mattress top.  Then a second vertical straight edge is placed perpendicular to the first and the "sag" is measured from the bottom of the first  straight edge.  This test is bogus because the material on the top of the mattress is basically stretched over the "sag" like a bridge over a canyon.  Thus a "sag" on a relatively new matress will never be detected by Serta's test.  

Will someone one please tell me how Sleep Train and Serta get away with this kind of fraud?