Eko needed no "call backs", he died at peace, having dealt with his demons. Eko didn't remain behind, he moved on to the afterlife.




The Sideways was a fiction in the afterlife created by the characters after they died and before they were ready to move on to their real afterlife. It's a mix up of shared meaningful experiences they wished to re experience and personal issues they wanted to deal with - for instance Jack placed himself in a situation where he would have a chance to save Locke, but also where he would have an estranged son and he would manage to turn this relationship around in a way he never managed to do with Christian (that was his old "I can't be a father to Aaraon because I'll be just like Christian" demon).

Ben is still haunted by some of his choices (what he did to Locke, and all his bad calls about Ale and gave himself new chances to make different decisions, like earning a meaningful place in Alex's life, not stealing it; like placing his own interests self-lessly after hers as a real father would have done.

Sayid dealt with his demons about the freighter events, at the same time re experienced his sacrifice to save Jin and Sun.

Jin and Sun wanted to live together some important events: Jin wanted not to fail saving Sun, they both wanted to live the moment when Sun saw Ji Yeon in the echography for the first time together, not apart and half estranged.

Claire wanted to re experience Aaron's birth, and so did Claire and Charlie. Claire wanted to deal with her demons about giving up Aaron and being abandonned - she wanted to make the choice again, and see if she would get the same support from Charlie and Kate, and Jack.

And so on.

A lot of people in the Sideways like Aaron, Keamy(and likely many others like Eloise, Widmore etc.) were not "real", they were creations of the others.

Walt, Eko, the real Aaron - they probably moved on "long ago".