Is 'Let Him Who Is Without Sin Cast the First Stone' Biblical?

[snopes]

When Dallas Theological Seminary professor Daniel Wallace examined New Testament manuscripts stored in the National Archive in Albania, he was amazed by what he did not find.

The story of the woman caught in adultery, usually found in John 7:53-8:11, was missing from three of the texts, and was out of place in a fourth, tacked on to the end of John's Gospel.

http://www.christianitytoday.com/ct/.../117-31.0.html