Welcome to Mac Forums.
Firstly, could you just check whether it's in the Applications Folder? If yes, then click on it and see if it opens.
If no, then it looks like, somehow, it got deleted. Do you have a system backup such as Time Machine? If yes, go into TM and select a day when system preferences was working, select same from Applications and restore. If you don't have TM, then have you a cloning backup such as SuperDuper! or Carbon Copy Clone?
How we might help from here depends on the answers to the various questions posed above.
It would help to to know which OS you are running and on which Mac.
Ian