> Can a modern phone contact a BT device without being manually paired (assuming it has cooperating software on the phone)? Yes. I manage IOT apps for android

> Can a modern phone contact a BT device without being manually paired (assuming it has cooperating software on the phone)? Yes. I manage IOT apps for android and iOS that do exactly this. You can write/read data to any bluetooth device around you that is advertising as connectable and has a GATT characteristic that supports it.