Here is my guess: The second photo you realized you had showed the subject holding the device used to take the picture sent to your colleague. You investigate

Here is my guess: The second photo you realized you had showed the subject holding the device used to take the picture sent to your colleague. You investigated that particular device and found a way to uniquely identify it's pictures based off some characteristic of it's photos, not necessarily EXIF, then scoured the Internet for photos with the same unique characteristic until you found one that revealed more information about the subject?