Oh no! I have heard of homeowners doing the cement down all drains back in the foreclosure waves of 2008-2011 but I had never heard of a contractor attempting this! Mostly because all of the contractors and subcontractors that I know are worried about their reputations, insurance, and contracting license. I would change the locks, repair everything, and keep all documentation then file a small claims case against him. I wouldn't bother hiring an attorney because little is likely to come of this but you mention he started an LLC he might have taken out handyman insurance etc that if named might pay for this.
I would definitely tell the people that referred him, as well as leaving a review under his LLC and personal names on google, yelp, and the BBB. I would also contact the state licensing board.
The chances of getting money from him in court are slim, if anything the negative reviews, notices from BBB, notices from the state board, then the notice from the court will force him to come to you to pay the damages and go back to hiding under whatever rock he scurried out from under. Even this has a small chance of working but coming at him from several sides at once might make him think you are far too much trouble to not just pay back quickly and get away.
SO LUCKY you are a local and this didn't happen to an OOS investor!! Other investors pay attention and make sure you never fire anyone with access to your properties.