We don't know, that's what we're trying to find out
Losing the story quests means just that - the story stops appearing. You only have recurring or side quests available. Usually this happens when some kind of trigger is skipped, or the logic breaks a bit. However, there are certain spots in the story that will cause the story to reappear. So if you lose the story, you can just avoid completing any side/recurring quests until you reach much higher continent maps, and then it's much more likely that when you complete a side/recurring quest, the story says "Oh! You're on that higher age's story now!" and jumps you there.
Even now, with Truth or Dare, that's essentially what we're doing. We're waiting at a place where we don't have a story quest (since Truth or Dare is a side quest) until we get further on the map, at which point we can trick the story into thinking we're farther along than we should be.
