German artist Gustav Metzger's work was rubbish literally. In 2004, the artist's installation Recreation of First Public Demonstration of Auto-Destructive Art was on display at the Tate Britain when a museum employee accidentally threw part of it away. How was he to know that the plastic bag of trash sitting next to the artwork was actually part of the artwork? The bag was later recovered, but it was too damaged to display, so Metzger replaced it (whew!) with another bag.
Metzger isn't the only artist whose work has been accidentally mistaken for junk. In 2001, Damien Hirst lost a pile of beer bottles, ashtrays and coffee cups (meant to represent the life of an artist) when a janitor at London's Eyestorm Gallery cleared it away. And in the 1980s, Joseph Beuys had a dirty bathtub scoured clean by a diligent employee in Germany who was probably wondering who had taken a bath in the middle of an art gallery.