you don't have to be consistent or anywhere near logical when writing fiction. Like, for example, you can have a lady who wasn't even pregnant when she went missing claim just three months later that she's the biological mother of a two month old, and people believe it.
I liked Lost, still glad I watched it, but the constant changing of what is or wasn't important was a bit frustrating. So many characters killed off just when you thought they were about to serve a purpose, and in the end the only purpose they served was as evidence that we all live and die. So many story arcs left untold.