First I suggest doing a search on your pc for all .pst files.
You may have files stored in another location besides the default.
Then if you have discovered more pst files, note the path and then try to
open them. You may have to attach them again if you have previously deleted
your email account and recreated it. Importing them also can pull them back
to whatever folder you designate.
You can also go to the control panel, select mail and you can then note the
path currently being used and any others data files present in the current
profile.