The convenience of a smart phone cannot be denied, and also undeniable is the inconvenience of losing one.
Both of the major smartphone Operating Systems (Google’s Android and Apple’s iOS) have a feature to help you find a lost phone. Via the internet you can put a message on the phone’s screen that says something like “$$$ reward, call 415-101-8528.” You may also remotely lock or erase the phone to prevent your personal data falling into the wrong hands.
Essential to making this find-my-phone (FMP) feature work for you is being ready to implement it as soon as possible, preferably in the first hour after losing your phone. Every hour that passes makes it less likely your phone will be recovered. To be ready to use the FMP feature you really need to do a practice run. Seriously! You will not be prepared for a real emergency unless you practice. To do this, hand your phone over to a trusted friend telling them to take it away and promise not to give it back to you until you have put a message on its screen telling them you have successfully used the FMP feature.