I’ve been rereading cases with Kid appearances in preparation for the upcoming Magic Kaito anime. Regarding the Magic Lover’s Murder case:
Sonoko tells Ran about this presumably cute guy, Doito Katsuki, that she’s been talking to about magic on the internet. It sounds like they’ve had lots of conversations and got to know each other some, even though Sonoko was (poorly) pretending to be a guy. He’s her favorite person in the chat group.
Sonoko gets to the magic lover’s meetup and is disappointed that Doito Katsuki isn’t attractive like she’d expected.
Sonoko gets knocked out by Conan so she can “reveal” the case, including the fact that “Doito Katsuki” is actually Kaitou Kid in disguise.
So despite the almost infinite breadth of the internet, Sonoko unintentionally manages to zero in on Kaitou Kid and have actual conversations with him.