Ok. Google is, as always, your friend. The trick is knowing some of the right key words.... like, in this example, offline installer.
Apparently, MS doesn't want to provide you with a direct download of Office Starter 2010 for offline installation. This doesn't mean it isn't possible.
So, have at it. Yes, I know you said you don't want to Re-download everything. So assuming you already performed a factory recovery and Office Starter 2010 wasn't there, this is really your only option.
That, or you could switch to Open Office or Libre Office.