Line workers had to put the broadcast sheet somewhere. The sheet was supposed to be collected at end-of-line for plant records. In the day-to-day of assembly, the sheet often ended up in the nearest cavity — under the rear seat, behind the back-seat upholstery, between the heater core and the dash, sometimes in the trunk or behind a quarter-panel trim piece. There it stayed, often unseen, for fifty years.
Restorers find them when they pull the seats. The find is part of why these cars draw the people who restore them: a paper artifact of the day in 1970 the line built this exact car.