To find your passport number, open the passport to the inside front cover and look in the upper right corner of the page. The number is nine digits long and is typically written in black ink under the line "Passport No."
To find your passport number without the passport available, you need to check the passport card that arrived with your passport. If this is not available, your arrival forms or check-in documents may have the number written on them. If your purchase an international e-ticket, your passport number is listed in the email itinerary and receipt.
To report a passport lost or stolen, call the Department of State. To replace a missing passport, make an appointment in person at a Passport Agency or Center. The new passport arrives in eight days or fewer. Once an owner reports a passport as lost or stolen, it is invalidated and cannot be used as identification or for travel purposes.
If your find your passport after reporting it lost, mail it to the address provided by the Passport Agency. You can choose to have the new passport cancelled and the old one returned; otherwise, the agency automatically destroys the old passport and sends you the new one.