I was catching up on my Wired magazines last week and found a LEGO reference. It says 817,600 LEGO pieces were lost at sea near England in 1997 while headed to New York. A search led me to this US News & World Report article, which puts the number almost 6 times higher at 4,756,940 pieces, and this Independent article which also says 5 million pieces. I guess these were bulk parts, sorted by type into big tubs, which were meant to be packed into about 10 different sets at Enfield. The different articles list a bunch of different element types lost, like witches hats and scuba flippers, and I also found references to a complete manifest of lost elements and quantities, but wasn't able to find the manifest.
I wonder if and how LEGO replaced all the parts needed to be put into the different sets?