Buyer has not received item that I posted. Had no tracking number. What to do now ...

[kerriannelee84]

I sold an item recently that actually sold for a lot more than what I originally thought. The item clearly stated in the 'postage & payments' tab that it would be sent Regular Aus. Post Parcel (which means no tracking provided). The buyer is now contacting me advising they haven't received the item. I have scanned and emailed my Aust Post receipt  to them. They have now opened up a case to resolve the issue. But, I just wonder where I stand... Obviously, there is no way of chasing up Aust. Post because it wasn't sent with a tracking number. I know on my end I am honest and have done the right thing, but how do I know if the buyer has actually received the item or not?? For all I know, they could have the item and are looking to get their money back also ... I just wonder if the Resolution Centre helps out both parties. I would hate to think that I lose that money I received for the item and have also lost the item as well.