I've had a few go missing for a while, but only 2 were ever LOST by USPS.
The first one was a Camillus MOP Barlow coming from Pennsylvania. When the box arrived on time, it was soaking wet and had a hole in it. Inside were a couple of pieces of wadded up newspaper but no knife. When the knife came through Dallas the day before, there was a MAJOR storm going on. The Dallas area got like 6" of rain and a bunch of very large hail. When the golfball sized and above hail hit, apparently all the mail clerks ran for cover and the buggies of mail on the dock got left out to get soaked. Then when the packages ran through the sorting machine, the box got a hole ripped in it. The knife was NOT taped down, just loose in the box. Out it went somewhere between Dallas and Austin. I sent the sell pictures, Seller filed a claim, and Seller refunded my money.
The second was a Official Boy Scout hatchet by Bridgeport. It was a rather rare one, with the original paint being a bright yellow and the company name, BRIDGEPORT, was stamped in an arch over the Boy Scout emblem, rather than along the poll where the name usually is stamped. The idiot Seller put the 1+ pound hatchet in one of those really thin cardboard "rice paper" boxed that hand held hair dryers come in, with a couple of balls of newspaper for packing and a small piece of tape on the top end and nothing on the bottom, just relying on the flaps wedging the bottom shut with friction. Naturally, the first time the box dropped anywhere in the USPS system, out the hatchet went. I got an empty box and the shaft from the Seller, Paypal AND USPS.
The third time I "lost" a knife, the box showed as having been delivered, but it never arrived in my mailbox at the PO, nor did I get a key indicating it was in a parcel locker. Insurance claim was filed by the seller, Seller refunded my money, the seller got her money from USPS and we all went our own way. SIX MONTHS later, I got a key in my PO box. Nothing was supposed to be coming in that week. When I opened the parcel locker, there was a box. On opening it, I saw that it was the missing knife, a 1985 ("I" date code) Western W84 (a small fixed blade). Went to the Postmaster and told him that the missing knife had arrived and asked him what we needed to do. He told me "Shut up and get it out of here. I don't need to mess with the paperwork."
The 4th story deals with a WW2 USN MK2 w/ NORD sheath coming from Hawaii. While tracking the package showed that it had departed Honolulu, after that it vanished. I thought MAYBE it somehow was sent surface instead of by air, so I didn't worry about it right away. As the time to file a claim neared, I did so. Insurance worked fine, seller and I both had our money. (The folowing was determined AFTER it arrived because I had quit checking on it after I got my refund.) Nearly 3 months after it departed Honolulu, it showed up as having arrived in Guam. Yep, that US Territory island out in the Western Pacific. A week later it departed Guam. A week after that, another mystery package in my box. Again, the postmaster told me to shut up and go away.
I also had a Challenge Coin take a 3 week trip from Honolulu to Fiji and then another 2 weeks traveling to California followed by Montana, Pennsylvania, New York, Indiana, Dallas, San Antonio and Finally Austin/Cedar Park.