This is really a continuation of my other thread from some months ago, where I was querying the disappearance of the query string in Opera's address bar. But that thread is now too old to contribute... [webmasterworld.com
I've just stumbled across this "new" (to me) option in settings > User interface > "Show full URL in combined search and address bar" (Opera 22, although it might have been there for a short while?). Woohoo!
Enabled this option now shows the query string (and protocol) in the address bar!