I would believe the answer to 1a and that lab has a good rep.
The reason most baby snakes don't pop with IBD is because they typically haven't had a chance to get exposed, especially when purchased directly from a breeder. Yours came from a retailer that cohabbed your baby with older animals so it likely was exposed there. It sucks but you must avoid that store in the future for the safety of your collection.
Personally I go scorched earth on stores like this, as IMO selling a vet bill is unconscionable.