39 CFR 762.41: Advice of non-receipt or loss, destruction, or mutilation.

(a) In the event of the non-receipt, loss, or destruction of a Disbursement Postal Money Order, or the mutilation or defacement of a Disbursement Postal Money Order to an extent which renders it non-negotiable, the owner should immediately contact the Money Order Division, Postal Data Center, P.O. Box 14963, St. Louis, MO 63182, describing the Disbursement Postal Money Order, stating the purpose for which it was issued, giving, if possible, its date, number, and amount, and requesting that payment be stopped. In cases involving mutilated or defaced Disbursement Postal Money Orders the owner should enclose the mutilated or defaced item with his communication.

(b) If the Disbursement Postal Money Order, which is the basis of the owner's claim, is determined to be outstanding, the Money Order Division shall furnish the claimant an appropriate application form for obtaining a substitute Disbursement Postal Money Order. However, the execution of an application shall not be required in the event the original written statement submitted by the claimant substantially meets the requirements of the prescribed application form.