Is modern art rubbish? The question hangs in the air like the stale smell of last night’s ashtray whenever art gallery cleaners stuff an installation into black sacks and leave it out for the bin men.

It has happened to Damien Hirst, Tracey Emin and other contemporary artists, and now it has happened to Milan’s Sara Goldschmied and Eleonora Chiari, whose installation Where Shall We Go Dancing Tonight? was swept away in its entirety by cleaners at the Museion in Bolzano, northern Italy.

The Museion after the cleaners had finished. Photograph: Museion Museum

To be fair, the museum’s cleaners were presented with a genuine conceptual challenge. They were told to clean up after an evening event – get rid of the empty wine bottles, that sort of thing. Goldschmied and Chiari’s exhibition, a comment on the corruption of 1980s Italy that tried to evoke the decadence portrayed in Paolo Sorrentino’s film Il Divo about that same era, was a careful recreation of the aftermath of a party with lots of empty wine bottles everywhere. You can see how the confusion arose.

Yet, far from being a condemnation of contemporary art, this habit cleaners have of mistaking it for rubbish is proof of its enduring vitality, or at least, indestructible novelty. Artists have been bringing rubbish, the stuff of everyday life that we use and throw away, into the gallery for more than a century now – ever since Picasso stuck bits of newspaper and chair caning to his paintings.

A sign outside the Museion tells visitors the work will be restored soon. Photograph: Museion Museum

Cleaners have presumably been throwing it away for more than 100 years, too. Most of the first readymades have vanished – modern icons such as Marcel Duchamp’s urinal, bicycle wheel, bottle rack and snow shovel were lost long ago and had to be remade in the 1960s. Were the originals simply chucked in the bin?

This art has been around for so long that, by rights, it ought to have become safe and cosy. In many ways it has. Visitors to Tate Modern stare respectfully at garden shrubberies or Duchamp’s (remade) pissoir. But still, the cleaners keep chucking stuff away – cussed working-class critics of modern art who are the last bastions of criticism now that Brian Sewell has gone.

Museums and artists don’t really mind. In Bolzano, they will just open another bottle. And why? Because as long as someone thinks modern art is rubbish, it is still provocative. It is still dangerous. Never mind that it sells for millions, and is enshrined with religious fervour in the world’s most powerful museums. Contemporary art may have all the hallmarks of establishment culture, but it is still Challenging, Subversive and Radical. It must be. The cleaners are still throwing it away.