Normally, Australian citizens are required to present an Australian passport when entering Australia. According to [Travel documents for entry to Australia](https://www.homeaffairs.gov.au/Trav/Ente/Goin/Arrival/Travel-Documents-for-Entry-to-Australia):

> Australian citizens have an automatic right of entry to Australia, and do not require a visa. Australian citizens need only to present the following documents to officers in immigration clearance:

>    - a valid Australian passport or other acceptable travel document
>    - a completed and signed Incoming Passenger Card.

> Australians who hold dual or multiple nationalities should hold an Australian passport and use it to enter or leave Australia, even when using a foreign passport overseas. The only exception is where they have been issued with an Australian Declaratory Visa.

The same page has this to say about the Australian Declaratory Visa:

> The Australian Declaratory Visa (ADV) is an administrative document that resembles a visa. It is issued in limited circumstances to Australian citizens who hold dual nationality, only if the applicant either:

>    - is a dual national under the age of 18
>    - has an emergency or other situation preventing travel on an Australian passport.

> The Australian Declaratory Visa is valid for five years from the date of issue, unless the holder ceases to be an Australian citizen, in which case the holder will need a normal visa to travel to Australia.

> Charges apply for this service.

The question for you is whether they would consider your situation an "emergency or other situation" that qualifies you to get an ADV. I would call the [Australian High Commission](http://uk.embassy.gov.au/) immediately and ask them what your best course of action is.