This doesn't quite fit with the "folder for everything" idea, but it does solve some problems.
My school includes business cards in the actor packets - with the name and phone numbers of
PM, SM, ASM, sometimes AD, and whoever else is important for the cast to contact if they are running late or don't know what the call is for the day. That way, even if they do lose all their pertinent paperwork (or some of it) they can still let you know in a timely manner.
The cards also fit in nearly everyones' wallets - which means they
really shouldn't lose it.