Who signed off on this event to have thought that having an NPC despawning within any time window was a good idea?

If this is not supposed to have been the case, and there's a bug/error regarding the NPC, then why has there not yet been an official statement?

If this was designed this way, firstly again who thought having a time-limited event have a time-limited, event-enabling NPC was in any way a good idea? Second, again if this was intentional why was it not clearly stated that this was the way it was meant to be?

As if the development team cannot disappoint any more than they have been, they just keep finding new and creative ways to let people down.