Generally, if an employee needs to miss work for any reason, including medical care, he or she could be fired unless:
1) he or she has and is properly using sick leave or other PTO he or she earned;
2) he or she qualifies for FMLA leave (or leave under a similar state law) and the employer is also covered (i.e. large enough; under FMLA, that means at least 50 employees); or
3) the employer specifically gave him or her permission in advance to take leave.
If you're in a probationary period, you probably do not have enough sick leave or PTO, and you would not seem to qualify for leave under FMLA (or a similar state law), which typically require a year of employment. Therefore, it is most likely the case that you could be terminated for missing two weeks of work without employer permission.