"I-I I was hiding from my playmates, they were fighting about who would play with me that day, I did that to avoid conflict."
Karna so badly wanted to find out how much Gandhari knew and where she learned this all about, He was 100% those girls would not going to reveal this outside at least not to anyone who was not his mother Radha or father Adhiratha.
They might tell them but those four would never leak it anything outside as they understand the consequences of such a news being leaked. He might have to change his identity and relocate to a different place for safety, which they never want to happen.
As for Gandhari knowing this? He did not care about as long as she did not go and tell his mother, This information was safe with her and the people present there.
So he honestly answered her but was still not convinced that it was enough for her to neglect his well-being.
