The man turned it down because his daughter already had a recorder, Blackfriars crown court was told.
The previous day, Irish traveller John Maughan, 40, had used two teenage accomplices to act as decoys so that he could snatch the instrument from under the nose of acclaimed musician Min-Jin Kym as she ate in a Pret a Manger at Euston station.
Not realising what they had, the thieves were spotted researching the violin in the internet café in Tottenham Court Road the next day.
Miss Kym, 32, who is signed to record label Sony BMG, bought the violin 10 years ago for £750,000. It is valued at £1.2 million but her insurance only covers the £750,000 she paid for it.