Wasn’t there a case where a guy put up a webcam at his « He Will Not Divide Us » flag, so 4chan narrowed it down by flight patterns and celestial navigation, and had someone drive around town honking his horn until they heard it. Then took the flag down and posted it on 4chan.
Yes, The Internet Historian on YouTube has made a series of videos about this: "HWNDU" (He Will Not Divide Us).
It started with a flag outside in a public place [0], followed by being moved to a flagpole in the middle of nowhere (the one you're thinking of) [1]. The flag was then moved into a museum in Liverpool [2], and finally it was moved indoors with a camera pointing at a plain white painted wall [3].
Beware: lots of memes and occasionally offensive language.
