I know you have them. I know we all need to know better ways to deal with them.
When the students have passed out the copies, I place all the extras in the correct file folder.
I even put tabs on the file folders so they can be flipped around to become weeks 10 - 18. This way I have file folders that can be both the week 1 and week 10.
Students can go look for extra papers and get busy on any owed work they might have lost, given to the dog to chew up, dropped in a mud puddle- you know what I mean, the list is endless.
How do you keep up with those extra papers?