Big bits of wreckage sink and small bits of wreckage spread over large areas. There's nothing sinister in not finding any bits yet.
Look at AF447, it took two years, but the wreckage was eventually found and the events (if not an explanation for the causes) was found. The experience of searching for that will surely help here, and a good part of the South China Sea is relatively shallow.
The "door" seen floating in pictures yesterday looked nothing like a 777 door. It didn't have a slot "window", it had a square "window".