Hahaha. No. Unless nobody the child knows knows that the child was in child porn. Including the child, he repressed the memory. And the repressing doesn't effect him negatively in any way moving forward. This way he doesn't know growing up that there is video of himself being raped as an 8 year old. And of course, nobody he knows ever sees the video or hears about it. And as you said, the person who sees the video never creates any demand for additional child porn, and never acts on his desires to have sex with children. In this scenario, sure it's fine.
It's fine in the same way where I can murder someone who turns out was homeless, had no family, was going to kill himself later that day anyway, and nobody found out about it. It's just fine and dandy.