In The Fellowship of Ring book, Frodo, Sam and Pippin encounter a party of Elves in the woods of The Shire, led by Gildor Inglorion of the house of Finrod. The Elves invite the Hobbits to stay with them for the night after hearing of their pursuit by the Black Rider. They stay at their camp near the village of Woodhall, as the Elves rest before continuing their journey westwards towards the Grey Havens.
Frodo asks Gildor if he had seen Bilbo since he had left The Shire:
Gildor smiled. 'Yes,' he answered. 'Twice. He said farewell to us on this very spot. But I saw him once again, far from here.' He would say no more about Bilbo, and Frodo fell silent.
From Chapter Three, Three Is Company.
I have always been a little unclear about this line. Where and when did this other meeting take place? Was it in Rivendell?