That was kind of weird of her to offer you a replacement, and then want you to pay more for her mistake. Oh well, there is another reason I won't go on the LA!
I would want to know the parents of the seedling in advance. A number isn't going to tell you anything about it. Would you get the right to register it if you want? The rules are normally that the person whose garden it blooms in for the first time is the one that is allowed to register it. Since it has already bloomed, that right would go to whoever had it when it bloomed the first time. I'm wondering if the seller, or the hybridizer, was the first one to see it, and if the rights to name it go with the plant. That would be something that you should find out in advance.
Seedling numbers are just numbers. They only matter when you register a plant. If you don't number your seedlings, you have to make up a number for them to register them. So really, if there were no records kept on which parents produced this seedling, you will know nothing about it. Most hybridizers number theirs, so finding out would be great. Just getting good genetics from two parents in one plant is worth it sometimes. And, it's very pretty!
Please let me know if I confused you!