hit a new tab if you're using chrome, right click on the tab and try to reopen closed tabs, it might bring it back up.
Ctrl+Shift+T does that
if it saves their session, that will bring them to a thank you page at the end. sometimes this will count as a second attempt at a survey, and can earn a rejection from a requester that didn't know what you were attempting to do
if it's one of those embedded code pages though, you can possibly find it another way. (I'll edit this to include the link-key page when I get my next one - just the page, not any survey completion codes)
I thought you could save the code key generation page itself, the frame.. but youcan't