In "Bad Monkey" by Carl Hiaasen, the story involves a significant clue related to the circumstances of a man's death. It was discovered that he had a particular item with him during the night he died, which provides important insight into what transpired. This key piece of evidence is a cell phone, found at the scene or during the investigation.

Furthermore, the cell phone is crucial because it may contain relevant information such as messages, calls, or data that can help establish the events leading up to the man's death. This discovery highlights the importance of technology in solving the mystery and advances the plot by uncovering essential details that drive the story forward.