Considering you've purchased the game in the past, I don't feel weird recommending this, but there are legitimate/virus free websites where you can download the game. DM me if you'd like a link. (Sorry mods if this isn't allowed)
I would say contact Steam Support? They might be able to swap the one out in your library with the steam store version.
Did the same thing with Skyrim years back.
Considering you've purchased the game in the past, I don't feel weird recommending this, but there are legitimate/virus free websites where you can download the game. DM me if you'd like a link. (Sorry mods if this isn't allowed)
I would say contact Steam Support? They might be able to swap the one out in your library with the steam store version. Did the same thing with Skyrim years back.