I have an area at the very beginning of my game that cannot be returned to later at all. It would make absolutely no sense in the context of the game for the player to come back once a certain point is reached. However it still is a very important area. I have hidden an item in this area. A very powerful accessory. It is relatively well hidden and is meant to reward players who take the time to explore right from the beginning. It is by no means required to complete the game. But it is still incredibly useful. But as the player cannot return to this area later, this is the only chance they would have to obtain this. Is this still fair game design?