You can look closely at history, but another thing that can work is to start going to the same site you used a private key by typing the address one letter at a time.
What the hell is that supposed to do? The data is not cached, we have already established that. Furthermore, you can't generate a private key from the address. That is not how bitaddress.org works either.
This is also unlikely, but you will see the URL's that you visited and you may see the private key as a string passed to the URL.
No. The private key is never passed to any server. It is all handled client side in javascript. If it were passed to the server through something like the URL, the site would no longer be used, people would tell everyone to avoid that site due to the lack of security.
Do us all a favor and not post when you don't know what you are talking about.