Feeling guilty

I wasn’t sure where to post this, but I would like some advice.

So back in 2010 I worked as an assistant at a daycare. I worked in the two year old room. I was 19, and it was my first job, so I was kind of quiet. I may have been too quiet. Well, one day the lead teacher got frustrated with a toddler, and slammed her down on her bottom on the floor. The toddler didn’t cry much, but it was kinda rough. Now 8 years later I’m feeling guilty that I didn’t say anything. I guess it’s because I’m a parent now. At that time I didn’t think anything of it. I guess it was because the child was fine. I left that job six months later for a different one. For that entire 6 months the child was okay. No bruises, broken bones, or anything like that happened. I figured since the child wasn’t hurt then she was fine, but now to this day, I often worry if what that teacher did is effecting her now. The child was two then, so now she’s about 9/10 years old now. I wonder if she’s having like back problems now. I feel so guilty for not saying anything, but she was ok at the time. She was still ok for the rest of my 6 months working there. It’s like it never happened. I guess I’m just praying that nothing is effecting her now. Could it be? This is probably a stupid question, but can broken/bruised bones hide for years? Do you think the child is okay? Help