Why doesn't the passing ship realize that there is someone on the island?

The passing ship likely doesn't realize someone is on the island due to the island's remote location and dense vegetation, which conceals any signs of life. Additionally, if the person is in a vulnerable or hidden position, such as sheltering or camouflaged, they may not be visible from the ship. The ship's crew might also be preoccupied with their tasks or navigation, leading to a lack of attention to the surrounding environment. Lastly, adverse weather conditions or time of day could hinder visibility, further preventing the ship from spotting anyone on the island.