What to do if I find a passport I'd reported lost/stolen?
Never travel on your passport if it has been reported lost or stolen. You run the risk of being stopped at border crossings, as Interpol keeps a record of all reports of lost or stolen passports.
If you are resident in Australia you should return the passport to:
Embassy of Ireland
Passport Office
20 Arkana Street
Yarralumla
ACT 2600