This is one of the biggest issues with the hobby/industry. When you pop a snake and see what some think are hemipenes, they actually are not. I had an experience years ago with a rather expensive snake (at the time). Guy told me he had a male and we agreed on a price. When I got the snake, it was a female. It popped and the everted horns were displayed. He swore it was a male, he said he popped it a number of times. But I had to have a vet call him and explain the difference. He was bummed but agreed.
Good Luck!
Jim Smith