I was looking around Galaxy could't figure out how to un hide a game, not seeing a way ...I am really liking this so far!

Go into the following menu: Filter -> Status -> Hidden
It's at the top of the screen near the search bar when you're viewing your library.

It could be easier to find, but it makes sense since you don't want to see those hidden games anyway.
From there you can unhide the hidden games.

Thank you

how_to_unhide_games on gog.com

A little update. It looks like there have been changes on the website and even instructions from GOG are out-of-date.

Now to unhide a game, go to your games library on the website and on the left corner just above the first game you will see a pull down labeled "My Collection" click that and you will see "My Collection, "Updated", and "Hidden" options. Click hidden and it will show any hidden games where you can unhide them the same way you hid them in the first place.

There is a way to do it from Galaxy as well, by changing the filters. But I don't use that so I am not certain on how. I suspect that is the method GOG now gives on their own help pages.

The "hide" function in Galaxy still works (or better does not work) the same way as it has been described before. Years later however it still is absolutely impossible to hide a game just for a certain platform. So the "hide" function for me is completely useless. When I want to hide my DRM'd versions of a game I don't need Galaxy to hide my GOG versions as well. Obviously Galaxy devs are too stupid or incompetent to see this problem and so this will probably never been fixed.

What is the purpose of hiding a game when there is a obvious only show hidden games in the middle of the screen.
I hide games to keep people from knowing i have that game how can i remove this compromising message?