Sure he could be telling the truth, and spent $500 for a 100% het pied snake with no papers.... and now he is almost immediately going to turn around and sell it for the price of a used xbox 360 (that can be had for $150 easily)
Sounds to me tho like he is a BS artist. I would have no issue with trying to BS him right back.
Tell him you took him to a ball python scientist named "mike cavanaugh" who with a simple blood test was able to genetically determine that it is NOT het for pied. Tell him you want a full refund or you are calling the police by 4:00pm today.
You may not get anything out of it, but at least you will sleep better tonight knowing that you likely scared the crap out of him.
but thats just me.....