I don't have the answer sorry, but I would certainly be ringing CS (more than once if necessary - seems like they don't do anything on first call these days from what you read on here) and getting them to check the Tracking info. themselves.  I do seem to recall a similar situation ages ago and the Seller needed an emailed report from Australia Post confirming the Tracking details.

Off the subject a tad, a couple of months ago I sent a Registered Large Letter to a Buyer and because I always check receipt of the Registered ones, noticed it was sitting at the PO.  So sent a polite message to the Buyer suggesting perhaps the postie had forgotten to leave a card and that her parcel was waiting collection at the PO.  No response. Next thing the parcel arrives back here and would you believe within days, the Buyer messages - 'Couldn't get to the PO to collect, please resend'.  Geeeez, it had only been there two weeks !!  So you think to yourself, do I ask for the postage costs again, not my fault she didn't collect - no, do the right thing, don't want a neg so resent at my expense, not even a thanks !  And to make sure she realized I had to pay twice, I put the original padded envelope into a bigger padded envelope to resend.  I suppose the good thing was, she didn't leave any feedback, so at least it wasn't a neg.