The rule about drawing from the next-highest available card pile applies to only that: Drawing through a Draw
effect (or action). If there aren't any qualifying cards in any opponents' scoring piles, Navigation will not have an effect on the remaining scored cards. This is implemented correctly on BGA.
If you think about it, the effect wording itself already gives away that it doesn't trigger the next-highest card – else, if it worked like you asked, Navigation would probably just read "I demand you transfer a  from your score pile to my score pile!" without mentioning age 3, since they would be affected anyways after there's no more age 2 cards.