"And the eyes of them both were opened and they knew that they were naked; and they sewed fig leaves together and made themselves aprons.
And they heard the voice of the Lord God walking in the garden in the cool of the day: and Adam and his wife hid themselves from the presence of the Lord God amongst the trees of the garden."
Genesis 3:7-8
They were ashamed of what they had done, so they hid themselves.
It doesn't say that when Adam and Eve ate of the Tree that they received total revelation of the depth of sin. It took man thousands of years to discover it.
Even after they sinned, they were still so pure that it would have blown most of us away.