It happens more than you'd think and it's not always the persons fault.
Books on hedgehogs are outdated.
Some breeders will give out incorrect or outdated information.
Pet store employee may not be trained to educate buyers.
Not everyone looks everything up online.
Some sources online are just wrong.
I don't think the op was knowingly doing something wrong. The best thing we can do is go with the assumption that any person that comes on here wants the best for their animal, and may just not know any better than what they are doing until they show us differently. Then give them the information we have in a friendly manner, and remember we were all new at one point.