Software Update Failed

Hi everybody,
I have been ignoring the reminder to update the software on my iPhone 4 when I open iTunes. Well I finally decided to update it last night & it failed & bricked my phone. It wouldn't let me restore on my computer I use to sync/back-up my phone because of some error message 1604.

So I plugged my phone into another machine & restored everything to factory settings & now the phone works. Now ALL of my settings, contacts, etc. is gone. How do I restore everything back to before I attempted to update? I'm assuming/hoping iTunes backs up the phone before it installs a software update???

 

Anybody?

Does the iPhone perform a backup before it does a software update?