Do they sell commerical policies that cover only certain trucks in a trucking business?

Do you have an auto insurance policy? TAke a look at it - does it cover every auto in your state? No. It only covers the LISTED autos.

So no, your employee isn't covered in ANY vehicle - unless they bought an "any vehicle" policy.

So, THAT dump truck wasn't insured. It was UNINSURED on the road. I happen to agree with you - I'd say he's just saying it to get out of the claim. I'd hike down to the office, and let him know you're taking him to small claims court, and adding in court costs and lost wages for your time in court.

Don't forget, BEFORE you do this, to file a police report at your local police station, indicating as much of his information as you know, and including his statement that the truck is uninsured. :D Make his life a little uncomfortable.

You sue the owner in small claims court, for the damage to your windshield.

Exactally the same answer above. Just because he does not have insurance does not mean he is not responsible it just mean he gets to pay it out of pocket. Also when you talk to the police, make sure to let them know the owner indicated that he knowingly operates an uninsured vehicle.