I know someone has my iPhone 4S, but?

I just recently found a load of photos synced to my facebook account from an iPhone I lost some time ago. Unfortunatley, I don't know any information about this person. I turned off my GPS locater to save battery power (ikr). If anyone has any ideas, I would really like to know.

Added (1). I already tried find my iPhone, but the GPS locater is offline.

Did you have icloud set up? You can trace it through find my iphone if you did. Also you can contact the police and they can help you now that someone is actively using it.

If you have Find my iphone installed than you just have to log in to one of your friends phone or mac, trace your iphone and call the police

Try logging into icloud.com and clicking find my phone and if it can it will show you a map of where it is.