Why was the question closed?
The question was closed because deliberately cross-posting the exact same question to multiple sites by the same user is discouraged. Therefore the slightly newer instance of the question was closed for exactly that reason.
You are right in that your question is not actually off-topic. However, the only way to close a question with a custom message is to close it as off-topic, even if this was admittedly a little inaccurate in your case. Though, in such cases the actual exact close-reason is given in the comments on the question, where Ankit Sharma says:
Cross post are not allowed here, you have to pick one place to ask this. You can keep it on sicfi.se only or can ask for migration here.
What to do now?
You can either keep your original question at Science Fiction & Fantasy or, if you really want it to be here, you can flag it for migration there, using a custom moderator flag and explaining that you want it migrated here. This will then migrate the question with all its possibly existing answers and we can integrate it into the newer version here.
I understand that this is a little complicated if you are unacquainted with all the intricacies of question migration and cross-posting, but it is ultimately necessary to keep everything in order and not have too diverging simultaneous versions of the same question.
How to contact a user directly?
If the user has left a comment under your post or made an edit to it, you can just prepend their name with an
@ in a comment. This will actively notify them of your comment.
Otherwise you can also visit chat, esepcially our main chatroom The Screening Room and try to get hold of the user. Especially moderators are quite often around there.
And ultimately, the most fruitful and public way to adress larger unclarities about the rules or the moderators' behaviour and seek input from the community is to bring it to meta as you did here.
As to your intentions, the original question has been migrated over here and integrated into the newer version. So everything should be sorted out now.