Wrong. He wasn't charged with unlawful contact with a minor, which does require the receiver of the messages to be law enforcement.
He was charged with *attempted* possession of child pornography, since he asked and admitted to asking who he believed to be a child for nudes, which is a substantial step towards to completion of the crime of possession of child porn.
And no, they dont get overturned. The only court case with pedo catching that involved anything getting overturned is Commonwealth vs Aguilar in Pennsylvania, where superior court overturned the DISMISSAL of a pedo catching case and actually REINSTATED the case and charges, and he was found guilty.