Restoring your smart mailboxes on mac os

Hi,

To my consternation I lost a set of smart mailboxes I had carefully constructed over the years, and have no idea why. They just didn't appear in my Mail client one day. I had not upgraded or made any changes to my Mac in a while.

I was not able to locate a backup library plist file. I was able to login to another mac and visually manually reconstruct these so I got lucky.

I was just wondering if there is a backup plist somewhere or how this important configuration file is backed up (if at all)?