It's a chain reaction that a lot of people get pulled into unknowingly. For instance: joe schmo sells a supposed 100% het pied to John Doe. John is a young person just starting out. He doesn't know how to research a potential seller/breeder. He doesn't belong to Bpnet or the fauna forums and has never heard of the BOI. He only hears his friends on FB talking about BP's, how cool they are, and how he can make $$ on them. He's also naive. Therefore he thinks he scored big buying a cheap het off of Craigslist with no real info.
He turns around and sells the snake to another person just like him but he believes he's selling an actual het. When things like this happen many people can get sc**wed and not know it.
This is why you only deal with people you can and have researched. Paperwork is worthless as anyone can create fake paperwork. It takes more than that. You have to check the BOI, Bpnet, etc.. Question other people who have done business with the seller and ask to see photos of the visual parent that produced the hets. It's very hard for other peoples photos to be stolen and used for this since there are some tried and true sleuths on the forums that can always find out if the photo is someone else's snake or not.
Really though, it doesn't even need to be that involved. Just buy from someone who is fairly well known that others will vouch for.
Snakes, Jeeps, Dragons, Nature, & Knives.. Makes my world go-round!