Can’t speak for any vehicles before 1996 but every plant I visited from 1996 and after used travelers so line personnel could select proper items for the vehicle. One sheet was on the engine, one on the body, windshield, maybe a few more.
As the vehicle made its way down the line these sheets were stripped from the vehicle and thrown in the garage.

They were never intended to remain in the vehicle. They served no purpose outside the plants.