In Season 5, when Sun, Ben and Flocke meet up with Richard and the rest of the Others, Sun shows Richard the 1977 DHARMA Recruits picture (with Jack, Kate and Jin with the Dharma Initiative that fake Christian gave her and asks him if he knows what's happened to them. Richard tells her he watched them all die.
My first thought on this was that Richard must have somehow gotten to watch the shootout over the Swan worksite during which the atom bomb went off, and incorrectly assumed that they all died during that conflict. However, in season 6, when we see Richard run into Sawyer in the jungle (who was present during the shootout), he doesn't show any real surprise as to Sawyer's being alive. An episode or two later, when he runs into Jack and Hurley in the jungle and leads them to the Black Rock for the scene between him and Jack over the lit stick of dynamite... He again doesn't show any surprise whatsoever that both Hurley and Jack are alive.
Did I miss something, or was this a complete oversight on the writers' part?