Hi Brett
It sounds like a pretty strange situation to me. If you still have not had any luck with getting the denture maker to provide the goods, then I'd be putting something down in writing. Make a copy of the receipt, letter from the collection agency confirming they were ready to pick up and any other relevant documentation. Then just put into writing a simple letter of demand, explaining you have paid for a product that you have not yet received and requesting that they be ready for collection within, say, 10 days or, alternatively, you are entitled to a refund. Add that if they do not respond or comply you will be pursuing your legal rights.
If you don't get any response or action from them on this, I would be taking it straight to consumer affairs in your State and having them handle this for you as it's completely unacceptable and against the law to have taken your money and never provided you a product.
Keep us posted with how you go
Anna