Try to find them in every folders in your outlook, if they are nowhere, I think you can import the pst file to your outlook agian, the mail must in your pst file.
If you still can't see your mail, I advice you to fix your pst file, it may be corrupted. You can use scanpst.exe to repair it or some third-party tools such as Advanced outlook Repair, you can google "advanced outlook repair " to get more information about pst recovery.
Julie