The WC insurance should still cover your shoulder surgery/recovery if the need arose from a work-related injury. If you need surgery for non-work reasons, you should still be able to continue your Group Health insurance at your own cost for 18 months under COBRA.
We offer general concepts, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.
if your shoulder injury is found to be caused by your work, then your employer's workers compensation insurer is responsible. hire a local attorney to investigate you claim. Under Missouri law, you would get a wc check while out for surgery even if you are out on a lay off.
It is unclear from your post whether or not the shoulder injury was work related. If it was work related, the worker's compensation insurance should still pay for the surgery and rehab. If it was not work related and health insurance is paying for the treatment, then you will need to continue coverage. Under the COBRA law you should have the opportunity to continue your health insurance through the surgery and rehab, but you will have to pay for it.