What happens if my parcel doesn't arrive and the seller said they lost the tracking number

[jessicajohnson2403]

I bid on an auction for a phone. As soon as they auction had finished I had one and the seller tried to cancel the transaction I declined.

I paid for the item and 5 days later I emailed the seller to inquire about when it would be sold. They replied tomorrow.

Then they shipped the item. It never arrived and the seller claims to have discarded the tracking number without ever sending it through to me.(Even though the postage was for parcel with tracking).

I have had over 10 items delivered in the last 10 days with no issues.

Hi jessicajohnson2403,gooodstuff95 recently opened a cancel transaction case for an item you recently purchased: red lips home phone.Reason for cancel transaction request: The seller says that you have purchased the item in error.

Click the "Respond now" button to accept or decline this cancellation.

If you don't take action by 18-Jun-2013, the seller will be able to cancel the purchase without your consent.

You can view the case anytime in the Resolution Centre.

red lips home phoneItem #271217053601End time:Saturday, 08 Jun, 2013 12:47:20 AESTSale price:AU $6.5...

I haven't been able to get a decent answer from them. All they reply is

Dear jessicajohnson2403,

you cant I have sent item out

- gooodstuff95

What can I do in regards to this?