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.
You should return the passport to the Passport Office Customer Care:
Our How to Apply for a Passport Guide takes you through each step of your Irish Passport application
You can track the progress of your Passport/Passport Card application using your 11-digit application number.