Verb
fall off a truck (third-person singular simple present falls off a truck, present participle falling off a truck, simple past fell off a truck, past participle fallen off a truck)
(idiomatic, US, euphemistic) Of an item of merchandise, to come into a person's possession without having been paid for; to be acquired illegally; to have been stolen.
He said he bought it at the markets but I think it fell off a truck.