If the marker suspects that there is another page to your response they send a message to the SM who is able to 'rebuild' the question including the extra page/s that weren't sent through the first time. Remember that a lot of subjects are now marked online so the process has changed from the past.
Right. I knew I forgot something.
I think after the first two extra booklets I got I was just in a furious writing mode and writing my student number on the paper. Ticking that box was the last thing on my mind.
You have to write the number of booklets you used on the student completion record and on the cover of the booklet. If they see that a booklet is 'two of three' they're going to know that you used another regardless of whether you ticked the box or not.