I'm very curious to see if you get a response, as I have a buddy that also had their designs used by GSG (very clearly and brought up on a developer stream) and they still never provided credit even after they were reached out to. It's disappointing but not terribly surprising to see this potentially happen again with your work.
Edit: To be clear I'm also not terribly upset, it's just a bit disappointing and I mean to say that it'd be nice if they'd give credit and let people know if they're going to use something.