So bummed and disapointed in the USPS....

I was eagerly awaiting the arrival of my new Hello Kitty Greetings cartridge from one of my favorite and trustworthy Ebay seller, Proudparents2005. I have ordered (or won) from many times and never had a problem. Until now. And of course my dilema always happens on a holiday weekend...Anyhow, I have been checking my mailbox daily for this cute little cartridge to arrive and nothing. It should have been here last week sometime, I thought. I just so happened to think to look on my Ebay page and see if there was any shipping info. I clicked on the little link called "tracking number" and to my surprise my, USPS claims my package was delivered on Feb. 7th...hmmm...Nope- i have not received it...I have checked everyday, 'cause I really, really want it! So bummed! I called my post office and they we no help at all! So rude. And told me that the carrier that works that route is off until Tues also. Im so not happy. The Postal guy basically told me i was SOL....because they have it as delivered and the Co. I bought from says they mailed it....Im so aggrivated about the whole thing. Stupid Post Office, this is not the first time I am missing mail. I am so untrusting of them and now my neighbors. I put a notice in my neighbors mailboxes that if they had mistakenly received my package to please put it back. I dont know what else to do.