I lost my pst file when i did defragmentation ?

hi, i will suggest you to use inbuilt tool scanpst.exe. If it helps you then fine. But if it fails then you can try stellar outlook pst repair. Once i had also faced same kind of situation. My pst file is totally corrupted. I used this software. It fixed my entire problem.

You need to restore your file using a file recovery software or you can extract your data and emails from an ost file.
If you want to recover your lost file then you need Kernel for windows data recovery software for the recovery of your pst file; or if you have an ost file then you need an ost to pst conversion software for your mails and data.