IMO if you do not hear from "Seller A" within 5-7 days, put them on blast. you might not be comfortable with it, but it may save someone else the hassle of dealing with this same seller down the road, and that's a victory in my book. any breeder/seller worth their salt in this hobby should answer quickly and honestly. i'd consider the lack of response as a worst-case scenario: the snake was flipped due to not eating, and this should be known.
i've never been in this situation so i have no first-hand experience, but this is what i would do.