It sounds to me like just one more of those dishonest builders you see on the TV programmes. I don't want to sound defeatist, but at the end of the day they often seem to get away with whatever they've done.
I wouldn't let that put you off, though. Hopefully, the building inspectors will pursue and eventually find this person and ensure that he puts things right.
Look at it this way: there are many people who have lost a great deal of money to these cowboys and never recoup any of it, so it could be a lot worse.