I would go through the following links to help you find what you are looking for.
If you are still unable to find your .pst
Search for *.pst in the C: drive (or your hard drive location) using the Search Companion. Searching for items is different depending on the Operating System.
Let us know how this goes. Good luck.
If YOU MOVED the pst file and you still have it, move it back. Open Outlook, close the pst first, then close outlook and move the pst wherever you wish.