They can probably 'ping' the phone to get a response for locating without having the phone make the user aware, any more than you are aware when it pings the site to check in.
They can, and they have.
I recall a missing-persons case a few years ago, in Ohio if I recall correctly, where a teenage girl had gone missing. Her phone was active, but she wasn't answering it. The cops could only get her general area from the information the cell carrier had, so they went to the area and pinged their way to her phone.
Unfortunately, she was dead when they found her, but the process does work. I'm sure this has been done other times with happier outcomes, but happy endings don't sell newspapers.
We develop somewhat-similar technologies for the military. You'd be surprised what kind of information you can divine from the weakest of signals carrying almost no actual information if you have the right kind of receiver, the right algorithms, and the right processor to crunch all the numbers. The actual performance numbers are classified, so you'll just have to use your imagination, but whoever said there's no more innovation in RF engineering never worked in my building.
Clever never dies.