(SOLVED) This item is temporarily unavailable - OS X Network Install
Because there are so many confusing posts about this subject I thought I'd clear the air. You do not need to download anything from another computer, backup, create a boot USB or anything else suggested to reinstall your OS X.
First let's start with how you got to this point.
In order....You
-Restarted Mac holding down (command + R)
-Clicked on Reinstall OS X (insert your version here)
-Signed in with your apple I.D.
-Get Error: This item is temporarily unavailable
1st Question: Why did I get this error?
Answer: The apple ID you used has never installed or downloaded an OS. ( Mavericks, Yosemite, El Capitan, etc.)
This Is probably due to the fact that you used an Apple I.D. that was made because someone bought an iPad, or iPhone, or iPod and never actually owned a Mac. Or if you did own a Mac then you didn't use this I.D. to install and update that Mac. Got it? Ok!
2nd Question: What do I do?
Answer: Type in an I.D that has been used to update or install an OS. That means call your friends, your mom, your distant cousin, etc. to get an I.D. that will work. Don't worry once you sign into it your friend who lent you the ID can change their password. No harm no foul.
3rd Question: Is this legal, what if I didn't buy the OS X?
Answer: Are you kidding me. Apple hasn't charged for an OS since Mountain Lion. Really, that's besides the point. The mac that you are on came with the operating system you are trying to restore. You are not doing anything wrong.
I hope this helped and feel free to not leave any comments so that the answer doesn't get convoluted.
OS X El Capitan (10.11.6), Network install