As far as my knowledge is concerned, if your phone is missing from your pocket after for eg: you get in a argument with someone or let it be any kind of distraction method used by the gang which has surrounded you without you even knowing it, and suddenly your phone is missing from your pocket, or if you entered a jam packed metro coach and your phone is again missing, then at that point you should understand that it is the work of professional gangs who will after 1-2 hours switch off your iPhone/Android after which it will never turn on, let alone your ability to track it using iCloud.
This is exactly what happened with my cousin. The phone was offline for a few weeks after she lost it. It then changed hands three times. No need to insert a sim card to verify the phone is working.
Even if you file an online FIR, as soon as you press the submit button, you might get a call a fewhours later from an officer to confirm the details, but after that you will never hear from them again about your phone. They are least concerned
It's not a question of least concerned, there is nothing to track as the phone isn't on the network.
Now the third party sold it to a student who switched it on to use it. He got it at a third of the price. This is when it showed up on apple's network. My cousin then informed the cops that the phone was live and a week later they tracked it down.
Had she not informed them about the phone coming online then it would have been lost for good.
So apple provides the tools to track the phone should it get connected to the network and it will at some point. Up to the owner to periodically check for it and do the needful.
Google provides no such facility to track the phone by IMEI. Only the telco's can do that and which network it eventually shows up on is anybody's guess.
You'd think after it was reported that the IMEI would be blacklisted and no sim would work. I'm not sure of this bit. Whether it still works but also informs the telco that its live. This is the only way for it to be found. Otherwise a blackisted IMEI that refuses a connection means phone lost for good as its inoperable in the country where it was bought.