Once you get the first hint, the "there is something nearby" message and the "X person is the closest to the ring" are completely unrelated. The first message talk exclusively about the closest hint and has nothing to do with the ring (you can find more "???" and get additional hints, but they are useless). The 2nd message is the only one you should use to discover the rings.
To make the ring pop, the npc has to stand right on top of it, and the "???" will pop. 1 inch to the left or right and the "???" will despawn. It's pretty easy to find the area where it pop, but making it appears generally takes 3-4 min. You don't have to talk to the npc to make it appears afaik, just need her to walk on the correct spot.
XI Wiki

