There is no mention of the reset/limitation anywhere in the text of the quests, nor any duration mention on the items that are purchased to start the quests.
The items stayed in my bag (I had the jet black feather and was in the process of working on goldens) but the quest itself vanished without a trace.
As far as I know, other dailies are limited in sharing by current daily - but don't vanish. Even the quests in Tol Barad are completible over a few days, as are the other dailies.
Either there needs to be something in the text stating "failure to complete before daily server reset will result in quest failure and require a new item to start" or a duration timer - something to alert folks. While the commendations to purchase are plentiful as drops, it's rather disconcerting to be attempting to do these with a hectic schedule and realize they can't be completed on a different day unless the commendations are re-acquired, the traps repurchased, and the quest completed then.
The odd part was the quest ITEMS, ie, feathers, did not vanish - after repurchase of the traps I was able to start where I left off, leading me to believe this behavior wasn't intended.