Somewhat similar happened to me once

2 Mexican teens: Van sold by US gov't had cocaine

"MEXICO CITY (AP) — A Mexican family says that a van bought at a U.S. government auction came with an unwanted extra: an undiscovered package of cocaine beneath the dashboard.

Sergio Torres Duarte, 18, and his 19-year-old friend Julio Cesar Moreno were driving to a soccer match in November when they stopped at a routine police highway checkpoint near the Pacific Coast resort city of Mazatlan. They say they were stunned when officers discovered a kilogram (2.2 pounds) of cocaine beneath the dashboard of their blue 2004 Toyota Sienna. Eight months later, they are still in jail fighting drug trafficking charges." Not a coincidence that that the same markings were found on the packages of drugs found in the car by US customs in 2011 before they sold the car.

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I once bought an IH Travalall for some parts for around $100.00. I bought the car from a guy who bought it at a customs auction for the motor, which he pulled before selling it to me. The headliner and door panels were torn out and the car had obviously been searched. For some reason I thought to pull up the carpet under the front seat and see if anything was under it, as it did not look disturbed. Beneath it was an old worn and stained envelope filled with cash. Obviously some past owner's emergency gas or tow money. Not a fortune, but it did cover what I paid for the car!