USPS Crap software made lose over 4000 usd

I am not actually sure if it is their software but according to the customer service person that I talked to my package tracking # was duplicated. My package was sent to the wrong address and they are doing nothing about it. They say that because the address on the box was correct and there is nothing they can do. I just contacted the seller to see if they can do anything but I am worried I am screwed