Dr. Notes

Did you use paid time off (e.g. sick days? vacation or personal days?) you had accrued or earned for the absence? Or did you simply not show up for work? If you used PTO, you may not be retaliated against for using it: if they are not scheduling you because you used PTO, you could file a wrongful termination lawsuit against them.
But if you simply missed work without using PTO, then unless you 100% complied with some other policy (like a "call out" policy) which would let you miss this many days at this time on this amount of notice, you may be terminated. (And having a call-out policy or the like is voluntary for employers: an employer does NOT have to let employees call out of work, even for emergencies.) There is no general right to miss work, even for medical reasons: if miss work without using PTO or adhering to a call-out policy, *if* your employer has one, you may be terminated or otherwise disciplined (e.g. suspended; hours reduced; etc.) A doctor's note does not matter unless the employer wants it to matter: the doctor has no authority over the employer.
(Note: Family and Medical Leave Act, or FMLA, leave is not available if you missed 2 days of work, even if you and your employer are both otherwise covered: FMLA only applies to medical conditions requiring at least *three*, not two, consecutive days out of work. For  general information about when FMLA applies and who is covered, go to the U.S. Dept. of Labor website.)