Well, that does come readily to mind..but it says in the article that the mother was surfing through Instagram and then came across her daughter's pic on a user claiming to be a bisexual cheerleader with 11 child porn sites hashtagged onto the post.. so that's how she discovered that her lil girl's pic was being used on a child porn site.
So, I wouldn't rule out exceptions.. :)
Good point, you are correct.