I've been reading of stories such as one where a woman was detained after trying to sell a moon rock. This made me wonder how do Moon rocks get away from NASA and eventually find there way into the public?
Tiny samples of two moonrocks (one each from Apollo 11 and 17), encased in plastic and mounted on plaques were given as goodwill gestures to the various countries of the world and states of the U.S.. Some of these displays were later stolen or misplaced, often due to lax security around the displays or instability in the countries hosting them.
Other moonrocks were stolen from NASA itself, either directly (by employees who had access to the areas where they were being kept) or indirectly (from employees or institutions who were authorised to possess them, generally for educational purposes).
The moon rocks are indistinguishable from everyday lunar metereorites. Any claim of this or that clump of dirt being an Apollo moon rock is solely based on whatever the person making the claim is able to present.