Moses' Speech Impediment

Moses goes back to Egypt, but there's a new Pharaoh in town. This is like sort of uncharted territory and it's not going to be an easy battle. Moses doesn't know how to work with this new Pharaoh as well as he would with the other one. The thing they never explained that I'm confused about is what people thought after he just disappeared because that was like the Pharaoh's daughter's son. But I don't know what was going on.