A London gallery is looking for a £3,000 brick by artist Gavin Turk which went missing and was replaced with a worthless equivalent.
Revolting Brick, signed by the artist, was substituted with one from a pile which exhibition-goers were invited to take from after their visit.
The replacement brick had "thank you, have a nice day, next" boldly printed on it, and was from the pile for visitors to take for free if they wished.
They don't say how long the switch took to be noticed, I'd guess days.
Mind you, the caption for the photo in the article is the best bit:
The brick is the eighth in a series of 10 created by Gavin Turk
He didn't create anything, a brick manufacturing company made it, he just scrawled his name on it in pen! Another case of the Emperor's New Clothes.