It sounds like you are an artist for the project, correct? Are you credited somewhere in the project? You should be able to still list the project on your CV even if you arent in control of the page on itch.io, I dont think most employeers would really care about that.
Yes, what that guy did sucks, but it doesnt look like its against itch.io's TOS and I cant see how it would effect your career in the long run. That said, you could always talk to a lawyer to see if you have a case here. I'm not familiar with Polish copyright law, so I have no idea if a situation like yours would be handled more seriously than it would in the states