41 CFR 102-34.135 - What do we do about a lost or stolen license plate?
You must report the loss or theft of license plates as follows:
(a) U.S. Government license plates. Report to your local security office (or equivalent), local police, to GSA Fleet when a GSA Fleet leased motor vehicle is involved, and to the Federal Government Motor Vehicle Registration System.
(b) District of Columbia or State license plates. Report to your local security office (or equivalent) and either the District of Columbia Department of Transportation, or the State Department of Motor Vehicles, as appropriate.