[Soundy]

It was that long before they even had the technology to find Titanic, let alone get anywhere close to it.

Considering the depth of the ocean where they're searching, and the sub-surface currents, anything that could float would probably be far from the final resting place by the time it reached the surface, especially if parts were breaking off as it went down. Depending on how it impacted, a large chunk of the plane could be on the bottom, meaning not a lot of debris making its way to the surface.