Restoring one system file from Time Machine backup

I have this file that I want to restore, that is a system file, normally stored on /tmp.

If I open Finder, and select GO > GO TO FOLDER

I type /tmp on the window and it opens /private/tmp (???? why ?)

Anyway, the file is not there, but the file was there 5 days ago. I open time machine and it shows me an empty window If I go back in type, but if I type the name of the file on the finder search box, I see several versions of the file (one day ago, two days ago, etc.). I select one of them, but the RESTORE BUTTON is disabled. I right click on a file and select RESTORE TO, but nothing happens...

How do I select a system file from days ago from a time machine backup?

Yes, I am sure the file is there.

thanks.

Unfortunately, you're not going to be able to recover that file using Time Machine. There are a number of files and directories that Time Machine does not back up—primarily cache and temporary files. This includes the files in the /tmp directory. The directory itself (minus contents) is backed up, because it is necessary for a reinstall.

The complete list of exclusions can be found in /System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.plist

ᔥ Devin Lane: Time Machine Exclusions

because /tmp is a symbolic link to /private/tmp

aka /tmp does not really exist