I had the exact same question. This seems like a much bigger crime than the story is letting on. Also, shouldn't this be handled at least jointly by a federal agency? I didn't see any mention of federal charges.
I feel like fucking with the Post Office is one of those things that sounds minor but can be a big fucking deal. Your petty theft just became a literal federal case, complete with a police force whose whole job is to protect the integrity of the mail.