Military or civilian? Link? Military satellites are usually designed to be hard to find and there location is obviously kept secret.
Missiles don't need satellite's.
Not so. There are dozens of agencies around the world that regularly track anything in orbit around the earth right down to the size of a small bolt. NORAD in the US immediately comes to mind and the Russians and Chinese, amongst others, do likewise.
There is nothing hard to find about the orbit of ANY satellite (operational or retired) orbiting the earth. There are various sources on the internet that regularly publish databases containing the orbits of all satellites of the earth. A satellite launch is not something that you can hide. In fact, amateur satellite tracking is a fledging hobby.
What is not always published (especially with defence payloads) is the exact mission of a particular satellite. However, even this is typically fairly easy to figure out by looking at the orbital parameters of the craft. Different missions require different orbits.
The Chinese have not demonstrated the ability to destroy a GPS satellite, however. The GPS constellation orbits at an altitude of 20000km with an inclination of 55 degrees iirc. That is a very high orbit (halfway to geostationary) and it would require numerous engine burns taking many hours (at least) in order to reach for a hunter-killer satellite.
Even if such an attack was carried out successfully, there are at least another two dozen GPS satellites in orbit that would still function. The Chinese definitely do not have the capability to provide enough boosters quickly enough to destroy enough craft to disable the GPS network.
Still, if they (or anybody else) were ever able to achieve the downing of the GPS network, that would have very dire consequences for the US military. Sure, missiles have inertial navigation but the fact is that the entire world is becoming more dependant on GPS navigation by the day.