302 HiJack - how to I recover?

[SeoPupil]

Hi Guys,

One of my sites got 302 Hijacked - to the point my site has lost it's SE position.
I've tracked down the rodent that put the redirect in place and he has subsequently removed it.
The problem is, my meta etc is still showing, but it links to his domain, and if click the link, it goes nowhere.
My sites has dropped off the search engines totally.

What can I do to recover my search engine position?

I was told if I add some new content to the home page, google will re-index... maybe...
I have around 30k unique searches for my site per month and really cant afford to write the entire site off.

How can I prevent 302 Hijacking on my other sites in future?

Any advice would be appreciated.
Cheers