When does Wes's mom find his drugs in The Other Wes Moore?

In chapter 4, Wes and Tony get into a furious argument over where Wes got the money from to buy a new pair of sneakers. Wes says he got it from working as a DJ in the neighborhood, but Tony's not buying it; he's sure that Wes has been selling drugs. Although Tony sells drugs himself, he doesn't want Wes following in his footsteps. As the argument heats up, he gets mad and punches Wes right in the face, hoping no doubt to knock some sense into him. Their mom, Mary, breaks up the fight, and Tony takes off, still furious over what's happened.
Mary had never wanted to believe that Wes could be involved in selling drugs, but she now starts to suspect him. But first she needs incontrovertible proof. She finds it in the shape of marijuana, cocaine, and pills, which she locates in Wes's belongings. Now it's Mary's turn to be furious, and she flushes all of Wes's drugs—with an estimated street value of $4,000—down the toilet.