The gate agents used to cancel these - ie write 'Used' across them in a pen or Sharpie.
I have a friend that would carefully remove the staple, hide the SSWU and claim it was already collected when they sometimes neglected to write 'Used' on them.
Or this friend would claim that they were removed at the last station...ie when connecting from YOW-YYZ-XXX- would say "my SSWU was lifted in YOW."
It was the best of times, but it was the worst of times!
