Yes, one person has that ship. No, you won't be able to get it off them. If you do find out who it is through IC means then you won't even get a reply from them if you send them a message.
Yes, there is only one and there will only ever be one until someone researches it once research and development is implemented. Providing it is on the tech tree.
Yes, that is what Unique means - there is only one. Much like the Supremacy, Fairwind, etc. Possibly it might be on the tech tree, though more like it would just be the standard Courier ship that it is based on, and not the super-dooper version of the Infiltrator.