Cameron Diaz flashed a smile as she returned to the set of Knight & Day in Austria yesterday. The actress arrived in Salzburg earlier this week and was joined by costar Tom Cruise, who was fresh off a stop in Long Island for his third wedding anniversary with Katie Holmes. Before jetting off to join Cameron, Tom sent a very lengthy and heartfelt thank you to the city of Boston for their hospitality and memorable duck tours as well as to the crew for their impeccable work.