How does Bud use rule number 118 to survive?

In the book, rule number 118 helps Bud avoid losing his cherished suitcase. To paraphrase, the rule states that a kid should give adults something to confiscate so that their attention is diverted from the one thing the kid doesn't want to lose.
So, Bud survives his short stay at the Amoses by using this rule. In chapter 2, Bud hits Todd Amos for calling him "Buddy" and shoving a pencil up his nose. To punish Bud, Mr. and Mrs. Amos take away Bud's suitcase. The suitcase is Bud's most cherished possession because it holds Herman E. Calloway's concert flyers, Bud's blanket, an old picture of Bud's mother when she was a child, an extra set of clothing, and a bag of mysterious rocks with writing on them. The suitcase is the one thing Bud does not want to lose.
So, he sets to work to convince Mrs. Amos that he is afraid to be sent back to the Home. He cries and apologizes to Todd. Bud gives Mrs. Amos the impression that the thing he fears the most is to be sent away. The reality, however, is that Bud wants to divert Mrs. Amos' attention away from his suitcase. Bud knows that he will lose the suitcase if Mrs. Amos ever discovers his true attachment to it.
So, Bud uses rule number 118 to avoid losing his most cherished possession. He also manages to free himself from the shed and to retrieve his suitcase after the Amoses fall asleep. With suitcase in hand, Bud makes his escape.