aside from my iphone app, is there an alternative way to locate the lost/stolen phone without using 3g connection where in fact we need not to use it.

Please help me find my iphone 6. I did try my best to locate it but when checking the Find my iphone app it is offline status because the phone is not in 3g connection but the location services (GPS) was turned on at that time. I activated my password lock just to ensure that no one can access the phone. I would be very happy that someone can assist me with regards on this matter. I had my serial number and the box with me as proof that I am the owner. Thanks!