What professional advice did you get before you left? Hopefully you:
1. Handed back your Medicare card?
2. Removed yourself from electoral Roll (and have not voted since), and
After you left for that FY file a 'Final Tax return'? These are the things necessary to be a 'non-resident for tax purposes'.
If so you have no issues. If you didn't and used your Medicare card since then you are partially liable at least-same with voting. They are privileges reserved for taxpayers. If you had income from property in Aus, you need to have filed a return-or may be subject to a fine. Having said that it is possible to file a number of years of returns at once (I did 7) through an accountant (I used SMATS and was impressed with their knowledge/service). Also you may be eligible for tax credits on return if you did have an investment property/ties-basically negative gearing against future income in Aus.