In Gen. 44:1-14, Joseph has his steward plant a silver cup in Benjamin's sack, then when the brothers have left, he has the same steward run after them and accuse them of theft. You can do that sort of thing when you're one of the most powerful people in Egypt. Of course, things go poorly for the brothers for a while, as they sputter and ask recite the age-old mantra of framed criminals everywhere, "how did that get in there? I've never seen that before!"
It doesn't work now, and it didn't work then. Especially not when you're dealing with crooked officials. It's a good thing Joseph liked them.