Please tell me that you checked to make sure that he has a license before you hired him? You will need to make a complaint with your stated license and regulations board or department. You can also file a complaint with your States Attorney, and check to see if he is listed with the BBB and also file a complaint with them. (Provide estimate of damage and cost of repairs from contractor)
Now since he is avoiding your calls this only makes me believe that he may be operating in your state illegally and is probably not insured or even licensed at all. If he is licensed he is jeopardizing his license by doing this. If he was insured and i received a call from a customer i would certainly been on my way to fix it, and pay for the damages 1. out of my own pocket or 2. With the use of my insurance.
If you have home owners insurance you can try to claim this on your insurance policy to see if it would be covered. Some insurances companies offer free legal representation to you.
You can also try to take him to court. if he is licensed, but quite frankly i believe he may not even have one, is operating illegally under someone else license, does not have any insurance Or all the above.
Theres no legit reason he would not make the repairs to your home that he messed up, Yes we are all human and even the best of us mess up some are very minor and some mistakes cost thousands. But this does not exclude him from any financial responsibility for the damaged he caused.
But be aware that suing him can be a long costly drawn out battle, this is also true if he's hiding. Eventually you will get there but i would suggest if the mold becomes a health hazard you fix this out your pocket and sue him for reimbursement.
I have seen and heard many similar cases most ending not good for the homeowner. Some get sued and just don't pay, or they have a hard time locating them because who they told you they were and there companies name does not even exist.
Further advice i would suggest that you check with your state to ensure that the person is licensed. Most states require you to be insured before they grant you a license. The license number can be found on there vehicle normally stamped on the side if not just ask them and look it up. You can do a search online to make sure that it matched with the company name operating under it.