well according to the trinity archives timeline, MX tried to push out terra so terra locked thier hearts?Kind of off-subject, but this has to do with the first post, and what everyone has been assuming...Terra did not take control back from Xehanort, it was the other way around. If you read the story for the Final Episode in the Trinity Report, it says that Xehanort unlocked...er..."their" hearts, so that when he fell into the darkness, Terra would be lost and gone for good (thus leaving Xehanort in control because he thought he was strong enough to withstand the darkness.)
So...yeah.
and their heart wasnt unlocked if it had been a heart wouldve came out of the body.