OK...I'm missing something. You have been off on WC for over a year and your employer terminated you for not returning to work? Were you released by ANY doctor to return? If so, then you should have returned to work.
Regardless, if you have been off for a year, it is probable that your employer cannot continue to keep you as an employee. If they would terminate anyone who was on any type of leave for a year, then they've violated no laws. They cannot treat you differently BECAUSE of your injury, but they can certainly treat you the way they treat others IN SPITE OF your injury.
If you want to file a claim for wrongful termination, which I advise against, since I see no case here, you have a WC attorney - let him get right on that for you! Seriously, you can file with your state's WC commission. The statute of limitations will vary by state, but yes, there will be a limitation - usually as little as 45 days all the way to 18 months.
Honestly, a doctor's note means nothing. If you were realeased to work you have to go back.
And, just for your information, the term "right to work" as patty indicated refers to union affiliation. The term your employer should have said was "at will," which means you can be terminated at any time for any reason or no reason, as long as it is non-discriminatory.
I am editing...I have reread your post, and it appears if I am understanding you correctly that they terminated you just days after you hurt yourself, so although you have been hurt and on WC for over a year, you were terminated soon after you hurt yourself? Is that correct? It doesn't really cahnge my answer, except to tell you that if you saw a doctor on Wednesday, you should have had the doctor fax a note to the employer advising them of your need to be off. Other than that, your employer is free to consider this unauthorized time - you were off for at least a week without giving them any detailed reason. And it appears to me, if you didn't see the doc until Wednesday, that you didn't report the injury immediately.
You did so many things wrong here that I can see.
I still believe you have no claim.
And just so you know...your ex-employer is free to tell prospective employers anything they want about why they terminated you, as long as it is true or representative of their honest opinion. So, if they want to tell people you were fired for unauthorized absences, they can. What they CANNOT do is mention any workers' compensation claims you made.