It made me go 'Ahhh' which is an effect I always appreciate.
Your style of writing fluctuated slightly and this meant I felt a little lost as to whom was speaking or where the story was taking me. After the initial meeting the diary entries seemed empty and dare I say pointless, which meant as a reader you almost lost me,but I perservered and loved the reveal....a ridge on the head, a tail.
Suddenly it was all clear and in some respects I would have left it there. However your final line made me laugh out loud and I intend to read the whole thing again to see what clues (if any) you have inserted along the way.