penders - 10:25 pm on Oct 17, 2013 (gmt 0)
I've just found this "Security @ Opera" blog post from a couple of months ago (25 July 2013) about "The Opera address bar" and this mentions the removal of the querystring in the URL:
After looking at how URLs were used today, we also decided to remove the query part from the visible display rip, as we did not find that it would help users understand where they were and what they were looking at.
...followed by numerous comments saying what a bad idea it is!
In fact I have come across threads from a few years ago on this same subject of Opera not showing the querystring! However, it has always been possible in the past to disable this "feature" in settings, to always show the full URL. (I guess this is what I must have done previously!?)