You should speak with an employment attorney about your situation. If you were injured or otherwise suffered some medical condition on the job or due to work, you may have grounds for reinstatement and/or compensation (including worker's compensation). Or if your condition rises to the level of a disability, you may not be discriminated against in employment. Or if you specifically used Family and Medical Leave Act leave, you may not suffer retaliation for so doing.However, if you were not injured on the job or by work, are not disabled under the law, and did not use FMLA leave, it may well be that your taking leave from work constituted voluntary resignation--apart from the examples given above, the law does not require employers to allow employees to take time off from work because they have a doctor's note. A doctor's note or doctor's recommendatio, without more, does not have legal effect. (Though you also need to review any rights you might have under any contracts or union agreements covering your job.)Therefore, you may be entitled to reinstatement and/or compensation, or you might not be; it depends on the circumstances. You need to review those circumstances with an employment lawyer. Good luck.