i bought this game the other day, had some issues installing it to begin with, one day it finally installed itself and wouldnt let me play as it was saying the game was "Not Authorized" now its completely missing from my list, as if i never owned it to begin with.... seriously wtf

Contact gog through the support page -> 'contact us'
http://www.gog.com/support

hopefully it won't take them too long to sort it out with you.
(Never heard of a gog game installing and then not running due to not being authorised - sounds like DRM )
Is this through the galaxy client?

That sounds like you might have bought the key from a fraudulent source. The source (often a stolen credit card user) got cut off along with all the keys he purchased and resold. Just a guess. Please don't take offense if it is wide of the mark.

not too sure but eh, hopefully this gets resolved

thats a weird thing, i have many GOG games and i never got this message.

You aren't supposed to get that message.

i know, i replied to say that i never got that message, because usually i am an unlucky fellow who gets nasty errors most of the time, lets call it my bad luck or so :D.
but since i havent got any here the error must be very rare.

Luck has nothing to do with it. If you buy your GOG keys from GOG then you will be fine.

If you never buy anywhere else than directly from GOG, you should never ever get that message. If you buy from unauthorized 3rd party key resellers, it's a hit or miss. More popular/expensive the game, the higher the likelyhood that key will be revoked.

Only authorized GOG keys sold outside of GOG are from the Wither series (made by their sister company CD Projekt RED), keys offered as kickstarter backer rewards and keys found on occasional bundle.

oooo, you mean reg keys for games?
i know about those error that might occur, i read a lot about it on the internet, it happens on more sites with reg keys.
i never buy registration keys for retail games, there are lots of sites that seem to offer keys , you pay you can unlock a game that you must download elsewhere.

These sites wont use a lot of traffic cause the downloads are not on their server, its only texts, very clever people.