QR code scanner

When using the built-in QR code scanner, if the code opens a web page, and the page requires the user to navigate away from that page (say, to authenticate), how is it possible (or not) to return to that page without starting the entire sequence over again?

For example, I scan a code and it requires authentication through another app (youtube). It appears there's no way to return to the previous page without re-scanning the QR code. Is it not using Safari to open the page?