Postal Conspiracy

Today I am a detective.  Not a real one, not even a TV, play or movie star pretend one.  Today I am hell-bent on solving the mystery of today's parcel.
The door bell rang at 8:30am just as I was serving breakfast; creamy porridge and the wafting smell of sizzling eggs filled the kitchen.  My mind was imagining the person on the other side of the door.  Was it a floral delivery?  An inquisitive neighbour?  My Godmother telling me I had won Lotto? 
No, it was just the postal delivery bloke, the parcel only man, the one in the van.   He held a decent sized box and I simply said, 'Oh thanks, I have been waiting for this.'  I signed his electronic hand pad and left the box on the table.  It was Mum's herbal tea ordered last week from Victoria. The sticker on the box said, 'Signature required.'  No drama there.
Hours later I heard the roar and the hum of the postie's motorbike doing his regular round.  The letterbox held a few letters and a small parcel.  Strange I thought (the detective in me), this is a registered post item only.  It is a small padded bag with two of Merv's prescription medications.  The parcel is delivered every month, if we are home we sign for it or else we receive a, 'you have a parcel to collect' reminder card and trudge down to the local post office with ID to collect it.
The detective bit - the parcel always has a registered post sticker on it, which alerts the postman to deliver it personally and get a signature.  The sticker had been torn off with only a small part of the corner still adhered to the front of the envelope. 
The issue - if the parcel had been stolen the medication could make someone very ill or even cause death if a child got hold of it.  Fortunately we have a padlock on our mailbox.
The mystery - my mind once again runs riot, was the postie too busy to knock on the door  (postie also delivers small parcels to the door, unlike the parcel bloke this morning).  Is he a rogue postie giving Australia Post a bad name?  Is he just lazy and thought he could get away with it?
He obviously never reckoned he would be up against the Aussie suburban Miss Marple! 
I am going to ask Australia Post to explain this scenario and I expect an answer.  It is important to us to keep our community safe.