How does the author use foreshadowing in Fat Kid Rules the World?

In Chapter 39, by the time they get to the concert, Troy is feeling a bit ill. His illness when nervous foreshadows problems in the future. It leaves the reader wondering what's going to happen if he is the one performing. At this point, he is merely a spectator. Even though his father warns him not to, Troy drinks. It doesn't take much for his new friends to persuade him.