Trying to trace Iphone
From Apple:


  If you have already configured the iCloud Find My iPhone service on
  your iPhone, iPad, iPod touch, or Mac you can use it to locate your
  missing device, display a message on its screen, make it play a sound
  at full volume (even if on mute), remotely lock it, or remotely wipe
  (erase) it to protect your privacy. Please see the following articles
  for more information:


The phone is pretty much useless to who ever found it.

But consider following as first step:
I just found your phone and it is locked and I have no idea to who it belongs, so there is not much I can do to return it. I could go to police station (but who has time to do that).
If you are so kind you would send a message to your phone with your contact information, email or phone number, I would contact you to arrange the return.