Why would you suddenly know where it is once you've got a coin? Wouldn't that make breaking the curse a little bit too easy?you got a point here, it would make sense to have other ways to find it. And if you are already cursed, maybe you should have access to it without that certain object?
According to the films, Isla de Muerta should be HARD to find. But it isn't; you can get there in five minutes if you know where to look.
Which is OK, I suppose. After all, it cannot be found, except by those who already know where it is.