folder vanished from .pst

Hello,

I have .pst file. I created few folders inside Inbox and created rules for
email delivery. About a week ago one of the folders vanished. I did not
delete it, and it is not in the deleted items. Basically nowhere could be
found. I used scanpst and did not recover any files and I think did not see
any errors. I created another folder with different name and edited rules
accordingly. Yesterday it vanished too. What that could be and is there any
tools I can use to recovered vanished folders and emails. Backup as a tools
was not implemented.

Thank you.