I once had a chip shipped first class mail to me that arrived at my house fully 16 days after it was postmarked. A few days before I got the chip, I go into it pretty good with the seller (it was an $80 chip and he didn't offer insurance even after I asked). I felt terrible about what I sadi to him when the chip ultimately showed up and had to eat a good 'ole plate of crow.....

If it went into the US Mail, sooner or later it will probably turn up. In the meantime, discuss it with the seller and don't burn any bridges....