The Dallas-based Cremona Society is suing a New York violin dealer after he lost a rare 288-year-old Stradivarius violin made in what is known as Stradivari’s “Golden Period.” The Society had consigned the instrument to dealer Christophe Landon in February, and in April Landon reported it missing. “I do not remember putting it back into the vault,” Landon said last week. He said he has tried hypnosis to jog his memory for possible clues.