FMLA requires essentially requires your employer to preserve your job for you, assuming your leave qualified for FMLA. If your doctor limited you to light duty work, your employer could reasonably say that you couldn't work if there are no light duty jobs. After that, you were cleared to return for regular duty. The fact that you were not hurt on the job makes no difference - that would only apply to a workers' comp claim. There may be a claim for violation of FMLA. You should contact an attorney as soon as possible to analyze your situation.
This information is provided for general discussion purposes only. Nothing contained herein constitutes legal advice, and no attorney-client relationship has been formed by the provision of this response. You should always contact an attorney in your area regarding local legal issues.