From the end of the note I posted on Facebook:
In the Flash Sideways, at the end:
*Where were Michael and Walt?
*Where were Rose and Bernard, who had both appeared in the Flash Sideways earlier?
Michael is still on the island, remember? Walt had no need for this alt reality when he passed, which is why he never showed up in it. Would have been nice, though, if he had...but if he did, then Michael would by necessity need to be there, too. And let's face it, fans HATED Michael lol...and that gathering at the end was as much for the fans as it was due to "logic".
Rose and Bernard were both there at the end...not sure how you missed them, they were showed repeatedly.
*What about Ana Lucia, Eko, and all of the other lesser characters? Ilana? Naomi? Arzt? I mean, Shannon and Boone show up...
Shannon showed up for Sayid's sake. Libby showed up for Hurley's sake. Anna Lucia was "not ready" according to Desmond. Why in the hell would Naomi need to show up? lol. She lived a grand total of something like 2 days on the island before being killed by Locke. Artz may not have actually existed in the alt/imagined world, but his being a teacher may have provided inspiration for that world.
Again, that ending scene was for the audience, not a roll call. It was to bring the original Losties from season 1 back together again, especially since half of them had died already. Picking apart who was and was not there misses the point of the ending entirely.