10 Incredible Things Mankind Has Managed To Lose
8. Some Of The Fabergé Eggs

There's no better way to show you're just plain better than everyone else than toting a Fabergé egg, one of the ovoid swag magnets created by the Russian jeweller primarily for members of the Romanov dynasty.
They're enormously valuable and almost synonymous with items of ludicrous, impractical monetary value for their own sake. Presumably we know where they all actually are, right?
Ha, nope. Seven of the fifty Imperial eggs are missing.
Most of the blame can be attributed to the regicidal bedlam of the Russian Revolution, where the treasures of the Tsars were spirited away to God knows where. Presumably some were stolen but it's just as likely they were just mislabelled by a revolutionary soldier ill-trained for inventory management.
One egg was last recorded in the Kremlin armoury in 1922, after which it went walkabout. Another of them was sold in 1952 to someone reported only as 'A Stranger'. Considering how famous and stupidly valuable the Fabergé eggs were, a lot of people seemed very lax in keeping track of them.