I'm not an atty but am a workers comp adjuster and wanted to respond from this perspective.
I was wondering if your employer turned in a claim at all to the comp carrier or did he refuse outright? The comp carrier really should have had an opportunity to investigate this claim. I have investigated several employee vs contracted labor and there are certain circumstances that determines the difference of each, and how they apply to the particular situation. Without knowing all circumstances it would be difficult to say it should have been covered or not, but it should have been turned in to the carrier and investigated. Also there is the issue of his auto policy covering your medicals, assuming there was medical coverages on his policy. Even if he cancelled the policy after the accidet, assuming the accident occurred during the effective policy period it would still be covered.
I would certainly seek legal advice to see what your options are. Keep in mind that there are statutes so I wouldn't waste much time. Good luck to you.