I remember years ago hearing about how the US mint misprinted over a million and had to destroy it (and on the Colbert Report, he joked about how them destroy it by burning it in front of poor people). We were talking about it at a party and someone asked, "surely they noticed? Why didn't they shut it down?" An engineer in our group said, "Have you ever been in a factory? It's so fast!" He worked in a toothpaste tube factory where you'd see hundreds of tubes come out every minute. If something went wrong, you'd have to wait for the whole pipeline to clear. Fab shops in China are even more insane.
I wonder if the mill would just sell those sheets at a reduced price as low grade/for non-visible construction or if they re-melt them down and run them again.