The geniuses at UPS (a wretched company, one I have had no end of problems with) lost the copyedited manuscript of The Amber Wizard when I sent it back to HarperCollins. They had no record of it being scanned into their system even though I confirmed it had been picked up from the shipping center. I was freaking out until it finally showed up in New York a day late. Somehow it made it all the way without ever being scanned.
I had no idea what we would do if it remained lost. I'm thankful I'll never have to figure that out.