"And I have NO idea how they found out, but I'm loving it!"
It's actually quite easy to do. These are very likely controlled docs, they get checked in and out. Not only from the room they are stored in, but from where they came from. Someone noticed something missing in the logs vs the security audit.
Think of it as having to sign for every piece of paper. Then check off every piece of paper when you return the docs. That's why it takes so long to do in the first place.
Backtrack and oh oh. Warrant time.
I find it hard to believe that there arn't copies or micro-fiche or disk copies of this stuff. If not, why not?
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Plus the whole pub has a number, and the number of pubs is kept in a very secure place.