You said the snake looked fine when you picked it out at the show?
The seller is going to replace the snake anyway, and pay for you to enter the show?
And the issue is...? I'm sorry the snake died, but since it died after a longish journey in your hands, I'd wonder WHY it died. I can't think of anything that would show a perfectly healthy LOOKING snake, that would kill it within 30 minutes of it arriving home.
What was the quarentine? You said "and before I put her in her actual tank I quarantined her to make sure she did not have mites or anything else." Did you mean you TREATED her for mites? Quarentining a snake isn't usually something you do before putting them in their enclosure, it's usually housing them seperately from any other reptiles for a long period of time.. 4 weeks? Longer?
