Does this person work in any way with a communications company or is very tech savvy?

Here is my eli5:

You can track cell phones by looking at the towers they are talking to. Cell phones are always in the background connecting and switching from tower to tower. Thee current tower(s) your phone is connected to is stored on the network so when someone tries to call / text you, the call / text can be routed to the right tower and you can answer.

Now during the process of making a call, the person calling can follow all the steps right up to the one that would complete the call and make your phone ring. By stopping before your phone rings, they can get the tower that would have made the last part of the call and your general location without you ever knowing about it

Source: managed and built a system that did exactly this for consumer measurement about 10 years ago using SS7 protocols. I think some of this might have been patched, but the general vulnerability remains if you have the right connectivity (very difficult for an individual, only providers should have this access).