In Kittens Game, my workshop seems to be missing the concrete button. I know I saw it there before. Did they remove it from the game? And if it's not removed, how can I get the button back?
To answer your question: it is not removed in game. I still got it and I got the latest version according to the changelog and due the fact I just saved + refreshed the game. I can craft it, both from the workshop as from the left side.
I don't know how to get it back. I assume you saved and refreshed, and have enough resources to craft it (2500 slab and 25 steel). You can make a bug report on Reddit if it still does not appear.