Unfortunately, from what I understand, it isn’t possible to hide 3d models or images or other resources you’re using in your pages. As long as the user can see it, they have access to it. What is possible to do is increase the difficulty for getting access to the resources.

This reply on StackOverflow does not have the exact answer you want, but has some ways of increasing that difficulty. The solutions are for image files but I think they are applicable to your models in some capacity: https://stackoverflow.com/a/21110248/9263761

It ends up being a trade-off between improving user experience with 3d models and exposing your assets online :/