I was having trouble reading it through the doc reader, but I was able to download it just fine and read it from there. It sounds about right for Cadogan, just the right amount of sarcasm mixed in with facts. I can maybe understand how your teacher would question its authenticity, not because your writing isn't as good as this usually is, but because there's a significant amount of worldbuilding already established through the story that is usually more than one might add for a short story. If your teacher keeps pushing and/or threatening to fail you for theft I would gladly send him/her an email explaining the details and verifying that it is in fact an original tale