As I do most of my shopping online and hence a major part of my life is spent anticipating packages...I truly feel your pain.
They would be liable only if the package was insured and the sender could provide sufficient documentation to prove that the contents were worth the insurance.
When you think about the magic of dropping a parcel or envelope off one place and having it show up someplace else, I'm impressed anything ever gets anywhere. But it does with such reliablitity that we almost forget the number of things that can go wrong.
I spent the holidays mailing a ton of packages to people. I spent at least a comfortable five minutes over coffee attempting to figure out why two packages, the same size, sent to the same address on the same day, arrived two weeks apart. (I sent them "parcel post," the "it goes if and when we have room in the truck" method, that's why. I finally asked someone.)
All you can do, xxxmalouxxx, is try and figure out if anything you've ordered never showed up. Or contact every single human being you've ever known in your life and find out if they'd surprised you with a gift.
And if you did buy something by credit card, charge it back.