This may be a very stupid suggestion, but have you tried calling it and talking to the robber? If not, simply report it as stolen. Text it saying you will report it
Hey MaliceRed, welcome back!
I think reporting it would be useless, because imo police or other authority wont take it as a serious problem and chase the thief.
For OP, if I'm not mistaken, Google has some way to track your lost phone, which you must have registered gmail account on the phone.