Can't redeem steam copy

[Athanaric]

I'm a Kickstarter backer (I think) that has traditionally always used the DRM free download option. I've recently looked into adding this to my steam library so I can stop downloading it manually, but when I try to use the redeem option the website tells me that the steam key has already been redeemed.  It's definitely not in my library though.  Is there anything I can do to redeem a copy on Steam?

[RawCode]

check your email as key for early bakers was distributed directly without current anti carding system.