The players guide has this quote in the description for the Time Lost campaign trait:
Your GM will be provided with additional information about this trait’s strange nature in the third adventure of Return of the Runelords.
Was this ever followed upon or did it fall victim to space constraints? I can't seem to find anything in part 3.
Not sure about that one, but I can ask my GM who has the book to find out for you. He did tell me around pg. 9 or 10 that there is a second on the Book 3 boost to campaign traits (use twice per book instead of one and ability score bumps), but I think that passage that you are referencing hinted at more.
I would imagine that it's referring to:
Spoiler:
Events 1, 2, and 3 of Book 3, since that's when the whole "time" theme of the AP is introduced. As well, it introduces the Steward of Stethelos, who makes their first appearance early on in Book 3. In addition, that book is when the timeline starts breaking, since that's when the players start taking penalties on Knowledge (History) checks.
Ah ok, that might be possible. I thought they might be alluding to something more specific. Thanks.