Call your insurance company first and get clarification on your policy, document who you spoke to, time, date, etc.... If you are told that your policy does cover these expenses, ask that they send this to you as you have 'misplaced' your benefit package.
However if they do not cover and have been paying all along they will be requesting their money back from the hospital and the hospital, inturn, will look to you for payment.
I would begin this right away as if they are paying in error you can go ahead and begin the paperwork with Medicaid as Medicaid has a time frame.
~Zig