this is sadly an intended function on Apple iPhone and Apple iPad. Due to how Apple cursors are used it doesn't auto move mice cursors in games like Terraria, so its not a bug to the game since its the same on almost all games using keyboard and mouse. There is a workaround to this however, Apple devices dont have the button in the scroll wheel bound to the system, so holding the middle click ingame will make the Terraria cursor follow the iOS pointer. its annoying but it works. The reason the sprite is hidden is also due to iOS having its own cursor (the circle that can navigate the UI on the device) however as of v14.3.2.3, that sprite can become visible if you tap the screen, but will disappear again when you use the actual iOS pointer (mouse cursor)