Never travel on your passport if it has been reported lost or stolen.
When you report your passport lost or stolen, it is immediately registered as such and cancelled. If you subsequently travel using this cancelled passport, 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 find your passport that was reported lost or stolen, simply send the passport to the Consulate.
Consulate General of Ireland
1 E Wacker Drive
+1 312 337 2700