Despite playing ~2,350 live concerts over 30 years, there exists some form of a live recording of every Grateful Dead show except one: March 17, 1970. A reward is offered to anyone who can procure the lost tape.
Grateful Dead show reward

Despite playing ~2,350 live concerts over 30 years, there exists some form of a live recording of every Grateful Dead show except one: March 17, 1970. A reward is offered to anyone who can procure the lost tape.