TBH, retrieving your phone is probably unrealistic at this point. Even if the thief turns on the phone so that it can be tracked using the Android Device Manager site, what are you going to do? Go there and confront him? That wouldn?t be safe. And it?s unlikely law enforcement would be of much help.
The most you can hope for is to be able to remotely wipe your phone.
If it?s been several days already, the thief has likely done a hard reset and swapped out the SIM. That means there?s no way to track it anymore.