The musical instrument turned up at a Swiss lost-property office two days later.
On Friday, a man left a Stradivarius violin — "possibly worth several million euros," the AFP reports — on a train. He had been borrowing the violin from a friend so he could play it at a birthday party.
Train staff searched for the lost violin and found nothing.
Surveillance cameras then spotted a passenger walking off with the almost 300-year-old violin at a different station. The police then launched an appeal for help.
On Sunday, the violin was turned in to a lost-property office in Bern.
Police didn't disclose the names of anyone involved, nor the value of the instrument.
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"Around 600 violins made by Italian master craftsman Antonio Stradivari are still in existence. One fetched about 11 million euros ($13.5 million) in a 2011 charity auction for victims of the Japanese tsunami," AFP reports.
In 2008, an American violinist left his $4-million Stradivarius in the back of a New York cab. The cab driver returned the violin to its grateful owner, who then thanked the driver with a private concert for 50 cab drivers.
(Photo courtesy AFP)