Lol. But seriously appeal to authority fallacy need not be only when the authority is outside their domain. For instance when authority makes a bad argument.
The dividing line here is that it's fallacious to argue that something is true simply based on authority. That doesn't hold where there are external cogent reasons for following that authority (eg. in this example: it's a difficult problem that's well studied by many, and the body of work has not yet yeileded an answer such that it's unlikely that a more casual hunch will do so).
