The name of the story is whoisbatman.com.
A few residents of Gotham City start a web site called whoisbatman.com, in an effort to learn Batman's secret identity. It invites people to submit videos from cell phones and security cameras, as well as eyewitness encounters, to crack the mystery.
Soon the site generates hundreds of thousands of hits and many submissions. Drones begin buzzing around the city, spotting and following Batman and the Batmobile.
As more evidence accumulates, it becomes clear that Batman's activities originate from the vicinity of the estate of one Bruce Wayne, who physically resembles Batman, is the right age, and is rich enough to do what Batman does.
Further, people who work for various manufacturers and shipping companies post tips that Wayne has ordered unusual parts, materials and forensic equipment that Batman would be expected to use.
Bruce tries to lay low for a while, but it's no use. The surveillance that has been unleashed against him is enormous and relentless.
Finally he calls a press conference and admits that he's Batman. He hangs up his bat costume one last time, then goes to work for the GCPD wearing civilian garb.