always have a pass security pass code that way no one can open your iPhone unless u jailbreak or something like that.
if you have a friend who's having an Ipad or Iphone you can track your phone by using ''find my iphone'' (i think it will show even if it's switched off) .just enter your apple id and password in friends device and it will show where it is.
one of my friends found his ipad that way.