During its recent gravity assist flyby, the Rosetta craft was mistaken for an Earth-threatening asteroid! From Sky and Telescope:

"The spacecraft was unknowingly 'discovered' on November 7th by astronomers in Arizona scanning the skies for Earth-threatening asteroids. They dutifully reported the 20th-magnitude blip in their images to the Minor Planet Center here in Cambridge, and the next day the MPC announced that the newfound object, now designated 2007 VN84, would have a close brush with Earth...

An observant Russian skygazer named Denis Denisenko was the first to point out that 2007 VN84 was, in fact, Rosetta. The connection had been missed apparently because no one from the European Space Agency had bothered to update the MPC as to Rosetta's recent whereabouts. And so on November 9th the Cambridge clearinghouse issued an Editorial Notice to declare that 'The minor planet 2007 VN84 does not exist and the designation is to be retired.'"

Well, maybe we'll keep the designation around... to refer to Rosetta's 15 minutes of minor planetary fame!