Oh, he can sue his employer (or the person with whom he contracted), the homeowner, Santa Claus, The Easter Bunny, even The Tooth Fairy (assuming he can serve any of them). He won't be successful, but he most assuredly can sue.
As the OP describes the relationship, he's not an employee.
In fact, he may not even be a contractor.
But, what do I know?
I'm just some anonymous dummy responding to the queries of anonymous blokes on the internet.
I'm not serving in the capacity of trial jurist here, just another dude on the 'net.
So, I'm not getting this twisted.
If you face a serious legal issue, a serious medical issue, a severe plumbing problem, or any other tragedy that can befall any of us; you should seek the assistance and services of the appropriate, licensed professional in your jurisdiction.
As far as workers comp, an employer in the construction industry (with ONLY ONE employee) is required to maintain WC insurance in Missouri.
In my experience, those who pay UNDER the table (or OFF the books), probably disregard other laws if they evade the tax laws.
http://labor.mo.gov/areyoucovered
Plus, MO WC law requires an employee to report his or her injury in WRITING within 30 days of the alleged accident! Failure to report your injury to your employer within 30 days may jeopardize your ability to receive workers' compensation benefits. Notify your employer in writing; the written notice must state the date, time and place of the injury, the nature of the injury and the name and address of the person injured.
If the "employer" doesn't provide you (the injured employee) a form on which to rpeort the injury, the state of MO does, right here:
http://labor.mo.gov/sites/default/files/pubs_forms/WC-280-AI.pdf
Every employer that has five or more employees must insure its workers' compensation obligations with an insurance carrier that is authorized to write such insurance in the state of Missouri by the Department of Insurance, Financial Institutions and Professional Registration, or meet the Division of Workers' Compensation requirements to self-insure its liabilities. Construction industry employers that erect, demolish, alter, or repair improvements are required to carry workers' compensation insurance if they have one or more employees. Railroad, postal and maritime workers are covered by federal laws, not by the Missouri Workers' Compensation law.