I think the sender of the package went to a FedEx store with a package addressed to something like 123 Main Street. The package information was entered into a computer system and a mistake was made; the employee who entered the data thought the "1" was a "7," for example. So the package gets delivered to 723 Main Street, the recipient opens it without noticing that the address is correct but the name is wrong (or maybe it just says "resident" or something). Meanwhile, no package shows up at 123 Main Street and the sender or recipient goes to FedEx and asks where the package was sent. At that point the FedEx employee probably should have said, "Tell me what address you wanted it sent to and I'll tell you if that's where we sent it." Instead, the employee says, "723 Main Street," and the intended recipient goes there to retrieve the package. Alternatively, the sender may have simply entered a tracking number online and brought up the address that was entered into the system. That seems pretty standard, and if the legal argument is that this practice is dangerous and should change... I don't know, that's a tough one. (And would going online to check a tracking number be part of the MO of smugglers wanting to leave no paper trail? I really don't know.)
This is all speculation of course, but I doubt this would have gotten as far as a lawsuit if the facts were simply that the sender used this woman's address on purpose and therefore had it all along.