What should I do if I find a passport I'd previously 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 living in Italy, you should return the passport to:

Passport officer,
Embassy of Ireland,
Villa Spada,
Via Giacomo Medici,
1 - 00153 Roma.
Italy.