Trade-in iPhone stolen in transit

Hi all, I recently bought a new iPhone and mailed back the old iPhone-an iPhone 12 Pro Max.

I followed the instruction email and went to one of the aus post stores to return my phone, they scanned my email QR code and printed out a label for the parcel, I gave them the phone and I thought it was all good. After a whole month my parcel finally arrived(aus post had a long Christmas break) but I got an email from apple saying that there was no device in the package!

I am furious and frustrated with the situation as you all can imagine.

I only have the receipt from aus post when I handed them the iPhone with the original iPhone package, the receipt does not show the weight of the package, I didn’t take any pictures before sending back.

what do I do in this situation? The phone was totally erased and removed from my device, can I request Apple to disable the device so that the theft can not be benefited from it?