In the early days of exploration, early centuries where people worked to map the world, there were constant omissions. One of the most common was the total lack of America in many ancient world maps. Then the Vikings and Columbus set sail, and suddenly it had to be added to the European maps.
With the more recent claimed use of satellites to map out the whole globe world, exploration has pretty much ceased under the logic that we've aerial views of every inch of the planet. But if that is not the case, we are in the same boat as those ancient cartographers that had never heard of the Americas and yet still believed they'd mapped the world. After all planes and boats only show us so much, and there are a limited number of flight paths. Might there be more land that has yet to be discovered, and won't be discovered for so long as the world labors under the delusion that the globe shows us everything?