Ah that really sucks on several levels.
Did he have any advice to keep the rest of your collection from catching it? ( I know they were in quarantine but I always panic)
It sounds as though your husbandry suppressed the symptoms but the follicles remaining inside could have compromised the immune system and let it get hold in the first place with the previous owner?
I can't see most keepers noticing that follicles hadn't been re-absorbed though so I wouldn't hold that against the seller if I'm honest.