I am super uncomfortable with the SA details having been released to the public. I totally understand Seth's frustrations with his ex, with the stepfather, with the lack of leads in the investigation into his son's disappearance. But man I wish he had kept that little tidbit to himself. if Sebastian is found alive, that info is now out there and can't be recalled.
I cannot imagine any child wanting the world to know about that event.
For that reason, I am not going to speculate about that past event or if Seth should or should not have done anything differently. Quite frankly, Sebastian having been victimized by another minor in CA when aged 7 is simply not relevant to the question we are faced with right now - WHERE IS SEBASTIAN?