When an Italian citizen is in an emergency situation (such as a tourist in transit has to start and has lost or was robbed of his passport) and he's not in time to institute the necessary investigation for the issuance of a new passport, post issues a temporary document-traveling (also called ETD Emergency travel document), which is valid only for return trips to Italy, the country of permanent residence abroad or, in exceptional cases, to a different destination.
To get it you have to show up at the consulate, which will issue after obtaining the following documentation and after ave experienced the findings of the case:

report of loss or theft of other travel documents, made at the consulate in accordance with Articles 46 and 47 and with the warnings by article 76 of Presidential Decree 445/2000
Two photographs (identical, full-face and in color, 35x40 mm format)
of the applicant's travel document
Receipt of payment of the cost of the document, currently € 1.34 and any shipping charges if the person concerned can not go personally to collect the document
And 'required to make the theft or loss of passport' to the local police authorities, for the purpose of facilitating the transit at the border.
In general it is advisable to keep in a different place from where you preserve your original travel documents, a photocopy of the most important documents (passport, identity card, credit card) to facilitate the procedures of assistance in case of theft or loss.
It should be noted that in the days before holidays and holidays such care could be foreclosed due to the closure of the same and deferred offices (except in proven emergency) to the first working day.