Having seen the Museum operations first hand, and met the staff, the mix-up is a bit of a mystery. Mine all arrived safely, by the way, though one package went to someone who is taking good care of them until they can get home.
In my case, what clearly happened was that the shipping invoices got switched between two packages. The package of Ian's swords I got was correctly labelled on the outside with the codes for the swords inside, and the shipping invoice in the plastic envelope stuck to it correctly listed the swords of mine that were mistakingly sent to Ian (in other words, the swords in the box that should have had the invoice). My suspicion, frankly, is that someone at Federal Express mixed up the invoices after accepting the packages from the Museum staff. They have to be taken in and out of the envelopes several times during transit, which is stupid because just this kind of thing can happen (I don't see why they can't put a bar-code sticker on the box itself).
I can't imagine that the Museum staff could have made such a mistake, and more than once, apparently. They even put my swords back in the exact same boxes in which I had shipped them (though most were identical in size and shape). Fed Ex, on the other hand ....

In the course of my work I often ship many boxes of documents at once to different parts of the country or the world, and more than once things went wrong. Once one box in a set of five or six ended up in a different country somehow, and another time a box of documents was delivered to the office split open, with footprints on the paper! The courier said he'd gotten it that way (yeah, right).
As many boxes as there were, who do you think is going to mix up and/or damage a box, the guys handling 20 or 30 who knew the contents were precious and fragile, or the guys handling 2,000,000 or 3,000,000 who didn't know and didn't care what the contents were? I just hate the see the Museum staff, who are so conscientious and careful, get the bad rap for how the shipment was handled after they sent it.