post office gave my package to someone else & told me to go get it from the person they gave it to

So I sent a package to my customer in another state. I always investigate packages that get lost. It was marked as delivered but not there. So I called in and a person on the phone told me they gave it to the wrong address and would call me back. Well they didn't' call me back and spoke to a new person who claim they have no idea who i talked to. I told them that the associate told me that they gave it to this address. And he said "if you know that why don't you just go and get it" . Well obviously I'm not the receiver and I can't tell my customer "go and get your package from a stranger" but is that the post office expects me to do? go to a stranger's house, put my hand in their mail box and hope my misdelivered is there??