@QuesTMaster good luck, you are dealing with people who don't understand that they should first contact Steam before they tell people to go there and use a "key" for this stupid game. They put up on there site "go to steam we are not supporting are own unfinished game anymore" yet Steam knows nothing about this. What kind of idiot does this. Or worse human garbage.
Here's a screenshot of Aven Colony on Steam right now. Literally thousands of people are playing it through Steam this way.
https://ibb.co/b8ZLBQ
Games can be on Steam without necessarily being visible in the Steam Store. Also, it's probably not a good idea to go calling people "idiots" and "human garbage."