I’ve ordered heaps from Tarte being delivered to a PO Box and never had an issue. They ship using DHL which transfers to Aus Post here and I have to sign for the delivery. I find that it takes a while (sometimes 4 weeks) but I always receive my orders. At the same time I work in a company where we seem to spend most of our time dealing with a dysfunctional freight network and I think most people would be shocked to know how incompetent the entire postal/freight system actually is.
Australia Post will get back to you advising what their records show. If you gave a street address and they left the parcel in your letterbox then they will deem it to have been delivered. Aus Post will only make payment if the parcel was insured, which I don’t believe it would have been. Paypal wouldn’t have protected you in this case either, because the sender can show proof that it was delivered – the advice from Australia Post.
I would suggest that you find out if a signature was required on delivery. The delivery drivers often just sign for it themselves and leave the parcel at your door or in your letterbox, but if it was required, ask them for a POD (proof of delivery). This will show who signed for it and you can argue that this is not your signature.
You can then go back to Tarte and explain the situation. Unfortunately they are under no obligation to replace the lost items since it appears the order was delivered and there are plenty of people the world over who try this on to see if they can get free products. They may however choose to assist you in good faith.
If you have no luck with them, and if you feel it is worth it, a last resort may be to make a claim with your credit card company. Different cards provide different insurances on all of your purchases and they may have an avenue where you can pursue a refund – you might just have to complete a form and provide evidence such as your invoice, the POD that doesn’t have your signature on it and your email communications with Tarte.
Good Luck.