Knowing the IP is pretty useless. The closest you can get publicly if you know that is the general region, but this app is already a nearby radius app, so you a

Knowing the IP is pretty useless. The closest you can get publicly if you know that is the general region, but this app is already a nearby radius app, so you already know that. If you have law enforcement powers you can try to get the subscriber info who was using that IP during that time period, but normal people don't have that ability. Even the article has to fall back to saying you have to just keep monitoring packets with that IP and hope the user uses some non-HTTPS web site that reveals their name. Although, honestly, most ISPs don't give you a static IP any more so the same user could be a different IP address multiple times a day.