Lost in the Jungle is an episode from Season 4.
It's early morning and Caillou is looking for Gilbert in his room. It seems Gilbert is hiding from him, but Mommy cuts the game short, saying that it's time for him to go to playschool. Caillou, however, keeps looking for Gilbert as it seems he's worried about him. Mommy lets him search around for Gilbert for a bit, looking for any clues that might help him. Gilbert's nowhere to be found, however, so they head off to playschool. At the school, Ms. Martin reads from a new book she got about the jungle. The kids all have fun making animal sounds and acting like various animals. Caillou imagines that he's playing hide-and-seek in the jungle. In the real-word, the class goes outside for recess. Caillou is playing hide-and-seek with Leo. He remembers Mommy's idea of finding clues and uses footprints to track Leo. Back at home, he finds Gilbert when he tracks muddy footprints from a rainstorm all throughout the house.