This should be considered a theft or loss of explosive materials. You must report the theft or loss of explosive materials, within 24 hours of discovery, to ATF by telephone. Call our toll-free number 800-461-8841 during business hours, Monday to Friday from 8 a.m. to 5 p.m. Eastern Time. On weekends or outside business hours, call our hotline at 888-283-2662 (800-ATF-BOMB).
ATF Form 5400.5, "Report of Theft or Loss—Explosive Materials", must then be completed and forwarded in accordance with the instructions on the form.
[18 U.S.C. 842(k); 27 CFR 555.30]