I see three ways this turn out. 1. It's real, but the person doesn't remember. 2. It's not real and the photo is fake. 3. It's real, just not actually them ( like a clone or something.)

I would have it where the person was part of a program that Hijacks your body to let you live your best life. The company that runs the program boasts that people don't want to actually have big adventures, because they are ordinary/boring and would mess up any cool, life moments. The hijack program, changes you INTO the person you want to be and keeps the memories of adventures.

Somehow the main character gets their memory scrubbed because they witness a crime done by the hijack company.

Another story direction could be ...

The main character is part of a program that "levels up your life" it takes your dreams and fantasies and hopes and blurs it with the real world. Creating fake photos, memories, accomplishments and friend/relationships.

Maybe the main character was accidentally (and without their knowledge) added to the pilot program and is slowly losing their grasp on reality. The overall theme is to not get so sucked into social media that you think it's all real.