To me, their explanation sounds completely plausible.

Personally I would have apologised and had another go knowing not to rush to get the quest as soon as you can.

I have to say though that it seems a suboptimal way to have coded this, much as I love scarab's work. For someone like me, who doesn't have info on a tap to find the items, or a group to gather them, I need a lengthy period to complete the quest. If I can't start it for ages I'll probably due before I complete it.