I can't redownload the game because it got erased from my purchase history, when it was available in twitch prime, I downloaded it and everything along with the free katana DLC and then I had to uninstall it because I had very little space, now that I had more space, I was going to redownload it only to find that it got erased permanently from my purchase history and asks me to purchase it again, I WANT MY FREE GHOSTRUNNER GAME BACK!!!!!

You need to contact support.

I tried and they wouldn't do that, why do you think I came here?

An ordinary user does not have the ability to give you your game back. When you get a game, the site sends you an e-mail of the transaction. You get this even if the game is free. Take a screenshot of the record as proof, and show it to support staff.

Edit: when did the site give away the game for free?

Twitch Prime gave the game away for free October of last year and I claimed it with the redeem code that I no longer have because it's redeemed and then downloaded it on GOG Galaxy and installed it, but then I had to uninstall it because I had no storage space at the time, then when I did, I found that it was removed from my library and order history

GOG staff rarely, if ever, reads forums specific to games. The support system is the only way to contact them for these matters, nobody on the forums can help you in any way like user J Lo said.

I claimed Ghostrunner via Twitch Prime, back when they gave out the code..
I won't be uninstalling it after reading this!!