recover a deleted file while the filevault is turned on If I turn on the file vault and someone turns it off and recovers the deleted file, does it recover to an encrypted state?
And if someone knew the password on my MacBook, could someone decrypt the recovered file?
The disk is what's encrypted, not the individual files.  So no, and no.
But if they knew a password that could unlock the FileVault, they don't need to decrypt the recovered file.