These interactions that Chris Martin has with fans appears to always be filmed by concert goers and posted on Tiktok/Instagram/Youtube. A couple of weeks ago I saw the videos where the camera in El Paso was turned on the fans watching from a hill next to the Sun Bowl. Martin sung a quick, funny song how they watched the show for free.
My guess is that someone (or many) posted it online asking if anyone knew this guilty-looking couple. Tiktok must have an algorithm that will quickly start to spread an increasing popular video, especially for a city. And it's the type of video that you would watch 2-5 times before swiping to the next.
EDIT: Everything is filmed nowadays and if it has any interest, it's posted online. There is zero expectation of privacy in public. And now that cameras are moving into glasses, it will become even more prevalent. We're not far from a person live streaming as they walk down the street, and AI identifying each person that walks by along with info about them. "Here's John Smith, and that doesn't look like his wife with him."