You would think that, the more valuable your musical instrument, the tighter you would make your death grip on its case whenever you had occasion to transport the thing. But even great musicians can be distracted, and this week, world-renowned violinist Gidon Kremer, preoccupied with a colleague’s cancellation of an upcoming tour, stood up and walked off a train in Baltimore, leaving behind his nearly 300-year-old Guarneri del Gesu, valued at $3 million. The violin was recovered in Washington by Amtrak officials, and transported north to Baltimore in time for Kremer’s next performance.