When does Percy start to realize the casino is a trap? Chapter 16

From the text:

I'm not sure when I first realized something was wrong. Probably, it was when I noticed the guy standing next to me at VR sharpshooters. He was about thirteen, I guess, but his clothes were weird. I thought he was some Elvis imper-sonator's son. He wore bell-bottom jeans and a red T-shirt with black piping, and his hair was permed and gelled like a New Jersey girl's on homecoming night.