It has to be turned on before a device is lost. Since Eric Root was responding to a user who has already lost the phone it is either on or it isn't and now the issue of if it is on, has the user tried looking?
If the device was stolen, and stolen two weeks ago, it is likely gone for good.
One more consideration is a balance between reporting this to the insurance company for what is an older phone with minimal value and running the risk of a bump in premiums, and somebody finding that phone and knowing about this service: Return a lost, locked iPhone, click here --> https://support.apple.com/HT211231