fall off a lorry

Of goods or merchandise, to be acquired by illegal or dubious means; to come into (someone's) possession without being paid for. "Lorry" is a chiefly British term for a truck. Primarily heard in UK. Danny says he has several laptops and phones he wants to sell for cheap—sounds like they fell off a lorry to me. A: "Jake's been peddling a bunch of flat screens for a great price." A: "They probably fell off a lorry then. I wouldn't go for them, if I were you." These prices seem a little too good to be true. You sure this stuff didn't fall off a lorry?

fall off (the back of) a lorry

(of goods) be acquired in illegal or unspecified circumstances.

The traditional bogus excuse given to the police by someone caught in possession of stolen goods was that the items in question had ‘fallen off the back of a lorry’.

1991 Time Out People buy so much stolen stuff that…you can…buy a video in Dixons and take it round the corner to a pub, say it fell off the back of a lorry and get 50 quid more than it cost you.