It took a French criminal investigation less than 2 weeks to find the wreckage. Accident investigations and criminal investigations are two very separate events. Accident investigations look for cause with the sole purpose of preventing future accidents. French criminal investigations determine cupability and liability. It seems that the previous (accident investigation) search 2 years ago may have been conducted in a half hearted manner so as to avoid providing evidence for a future criminal investigation.
More info on the discovery here:
http://www.telegraph.co.uk/news/worldnews/europe/france/8425600/Air-France-plane-wreckage-found.html