Please fix this.
I have a similar problem with another game (Alan Wake's American Nightmare) for exactly two months, but there is still no any reaction from GOG.
I'm not an expert, but it seems to me that something is wrong with the database from which GOG Galaxy 2.0 imports the information about the games you own. I have a reason to think so because I did a fresh install of GOG Galaxy 2.0 on my laptop, where Galaxy had never been installed before, and got exactly the same result - the game is still missing from my library. It definitely doesn't look like a problem on the user side.
You can try to create a report on Mantis, but don't put too much hope in it. There are hundreds of reports on Mantis (including mine) and only 16 of them have been resolved. (: