Share your experience!
I lost my Sony Xperia u, how can i track my phone and prevent any misuse of my mobile contents?
have you installed any antitheft apps on your phone?
if you have enabled location reporting & sharing with friends you can check your google account for location.
otherwise it is impossible to do anything, to get it back or modify its contents.
if you have written IMEI of the phone you could report it to your provider and police, I think they could locate it that way. Good luck finding your phone!