Here is a screenshot that shows missing sudo command. How do I restore it? I am not a linux expert, so please keep the answer simple!!
MacBook Pro with Retina display, OS X Yosemite (10.10.1)
The command isn't missing, but you do have a problem.
Knowing Linux might be helpful, but knowledge of Unix would be much more useful. Especially for whatever it is you need to use sudo for.
Regardless, your installation is corrupt. Backup and reinstall.
If it's missing then what happens if you simply enter "sudo" then press RETURN? When I try sudo -s I am immediately in a bash shell, which you are not. Normally, if you enter the command in Terminal you should be asked for your admin password. That doesn't appear to be the case for you.
Its not missing, it simply cannot determine if your user is allowed to sudo since it can't find any sources. This is usually an indication of a corrupt installation.
Linc Davis offers more insight in this post:
sudo command missing from Terminal app
