Complaint re missing T-shirt Order.

This is the only place I can find to message you about my complaint.

In early September, I purchased two different T-shirts, paid for with Paypal. I was told to expect delivery in about two weeks. As I’m in Australia, I gave it a month before I began to be concerned.
Finally one (only) T-shirt arrived! The second, and more expensive one, has NEVER arrived. It is now almost 2 months since I ordered them. I’ve never received anything (email or whatever) to suggest it is delayed for any reason.

I’m even more concerned, as at the time, the exchange rate between the US$ & AU$ was at an all time low, so I actually paid a LOT MORE than would seem fair for the two shirts.

PLEASE… how can I trace my missing shirt?!? Or receive another in its place?