Hello! I completed this quest with 45 minutes remaining on the timer, hearthed to return back, and discovered it had reset and no longer counted as complete. I went back out to the area just-in-case I’d somehow misread the completion bar, but when I got there, the bar and World Quest no longer existed, as if it had been complete.
I can’t turn this in, unfortunately. 
And would love some help. Thank you!
If for whatever reason the Calling failed to acknowledge the completion of the world quest, or you cleared the WQ before obtaining the appropriate Calling, the option should still exist to clear one of the two zone dungeons to get credit.
In the case of Bastion, that would be Spires of Ascension or The Necrotic Wake. I believe any difficulty should suffice.
I appreciate the tip! Alas, I did this with only a little time left on the clock. I doubt I’d have been able to get a group together to get it cleared in enough time. But it’s something worth noting in the future, to give myself more time if able. 