So I log in today to play some Witcher 3, but as it turns out GoG reckons i dont have the game installed anymore? Even though ive played it for about 15 hours now? how does this even happen and how can it be fixed in such a way that it doesnt happen in the future?

I saw a thread earlier where someone said that this happened to them. Out of fear, I made copies of the game and save directories :/

Did you install TW3 via Galaxy by chance, and is your installed games folder located inside the Galaxy folder? I had this issue during alpha testing and was told about the reason and given a solution from GOG themselves.

If you did install via Galaxy, make sure your games install folder is outside the Galaxy folder. For whatever reason when Galaxy updates, it purges every folder inside the Galaxy install location. This includes games and any save files that are present. Luckily TW3 stores it's save games in a different location in My Documents.

*If you didn't install via Galaxy or your install folder is already outside the Galaxy folder, then I'm affraid I can't be of further assistance.*

Fixed the problem but yea deffinitley making copies of the game now just incase. I was so afraid I was going to lose all my saves aha.