Welcome to Male Survivor and our F&F forum. We have a great group of partners here and I have learned so much from them. You may find sometimes that it takes a bit for people to notice a post, what with work schedules and so on, but hang in there and you will get the support you need.
I am so sorry you had to see someone being abused. I take it this was when you were young. Please don't blame yourself for not saying anything, if this is on your mind. There are a million reasons why that kind of thing can happen.
I can see why you would wonder if you were hurt as well. For exploring this, especially if you have no clear memories, I can't emphasize enough how important it is to be working with a professional therapist. A T will take you through this troubled territory with as little new pain and trauma as possible.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)