Atsuku was famous, but that was only true among light novel readers.
His reputation as an author didn't extend to normal people like the police or anything. They could've just searched the internet to find Gaiasinfo, but Atsuku had checked the website and didn't find his name.
It was as if his name was deliberately hidden by the website owner.
In the time he stabilized himself, Misaki had also hacked into the pirate websites and deleted all data they had on Atsuku's novel. She couldn't do anything for those with the physical books, but those people surely understood the dangers of revealing the information unless they were stupid enough.
Knowing this, Atsuku used this to his advantage to talk to Detective Motoki. According to Misaki, he was someone with a high sense of justice and could easily be swayed by new information and the safety of civilians.