LA had a "no garbage" policy. Once the cars were built, the need for broadcast sheets was over. Most of the LA sheets were apparently just tossed out.
For Hamtramck cars, the sheets in the bucket seats are usually the "wild cards". The reason is that once the order was filled in the trim shop they would slip the broadcast sheet inside the seat, put the plastic back on and it then went down a conveyor belt to the main assembly line.
Since the front seats were delivered to the main line with the backs on, there was no way to know if the sheet inside it matched the car it went into. The assembly line workers just grabbed the closest seat the right color and pattern and they bolted it in.
I have also heard of Cuda sheets found in Challengers & vice -versa, as well as Duster sheets found in Challengers.