Never travel on your pasport 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:
Embassy of Ireland
Cda. Blvd. Manuel Avila Camacho 76-3
Col. Lomas de Chapultepec Sección I
México D.F. 11000
Main tel.: +525555205803