Murphy and the police couldnt find it, but that doesnt mean he couldnt get supernatural help to do so. Just like Mab found his Amulet. I was just saying that it could be possible, not likely. And I dont think it has to do with his blood being on it either. I think it is just a connection or significance with how influential the person it happened to kill was. And even Odin told Dresden that he had been dead and came back again. I think if Jim wanted to use it as a device the logic would hold up, however, if he did it might protect Dresden in the end just because it was his own killing bullet...