OP - YABU, probable the 2 year old asked and was given a truthful response.
lilyjen - I'd be willing to bet money your 6 year old knows more than you think, or perhaps more appropriately - thinks more than you know. I'd also be hugely shocked if nearly ALL six year olds had not been through or were not currently going through various playground discussions about babies, conception and puberty. Lots of school age children have got pregnant mums, new baby siblings or pregnant family members or friends - this rather precipitates the barrage of questions. I agree that if your dd is not asking you that is rather worrying and suggests she might have learned you don't want to give her the answers.
I think it's both nice and necessary to share your pregnancy and birth with your existing children. My children have really enjoyed looking in the baby book since 6 weeks, learning about how babies are made, how they grow and how they are born. They are very comfortable and secure in what is happening and excited about their new brother and sister's imminent arrival.
They have really enjoyed going to some of the scans to see the babies on the screen and it has prompted them both to ask lots of different questions about various things to do with sex, conception, pregnancy, labour, birth and puberty.
6 years old is very late to be getting your first information about all these subjects IME. If you haven't spoken to your children about these things by then they will have gleaned information from the schoolyard and we all know that children like to sensationalise things to impress other people. Who knows what the child'll think then?!
As for high school musical?! That vile rubbish is a far more negative influence on a young child than the simple truth about the beginnings of life IMO! It's hardly a sign of innocence and good parenting to have little girls modelling themselves on over sexualised, fame hungry, teenagers.