That really is awful, it amazes me that just a signature is all that's needed these days, surely the courier companies must start using a way to see the recipients id.
As painful as this is, the sender must get in touch with the company used to send the bass, it is their fault that he didn't knock on your door to let you receive the goods. They will show you a POD but that is useless, have you seen some of them digital displays, my signature looks like a line. You should get your money back as long as your persistent and you did include insurance. I feel for you though, that bass is in some oinks hands grrrrrr