The main litmus test for most is feedback on the BOI... You can search for posts already about the person, or you can post asking for feedback on the person in question. Usually if there are multiple negative statements about a breeder, I won't consider purchasing from them.

You can also post on the feedback section here on the forum and ask about people you're interested in.

Have you tried contacting this breeder about the problem and if so, what has been their response (please don't mention names in this section of the forum, or this will get bumped to the feedback sub forum)? The halmark of a good breeder isn't only selling good animals, but also fixing their mistakes, whether they be shipping issues, mis-sexing a snake, or selling a sick animal accidentally. A good breeder will care about their reputation and will make things right.

If you haven't checked out the BOI, do so and read up on your breeder. If you haven't talked to the seller about this, then contact them and give them a chance to help you. If they refuse, you may have to post about them on the BOI yourself.

Good luck with your current snake and I hope he makes it.