I'm not a mother of a survivor, but I had one - the entire time I hid the abuse from her.
We DO hide things, and we hide things very very well. We become proficient in acting and protecting you from our truth. We feel you can't or ought-not deal with such ugliness and images of your darling son. As for fathers, we have so many other solid reasons to shield truths.
Just wondering, if you care to share - What is he getting for help right now?
Imaginary friends are people too!