No, that's a big GUI faux pas, at least in a game with this kind of minimalist GUI. I learned very early on, as a software developer, that it's usually better to disable than to hide GUI elements because it makes the interface easier to navigate and get used to.Then hide the map icon when not at a location where it is functionally available. Duh.
The big problem right now is that the icon is too subtle and unrecognizable. It will look like an actual map at some point, which will help a great deal. Not only will people more instinctively understand what it is, but its size and colors will mean it becomes much easier to see when it changes between enabled and disabled status.