Bluemann is incorrect in his reasoning, though he ultimately reaches the right conclusion.
There is only one state where the so-called "probationary period" has any legal meaning, and that state is not Georgia. While it is true that your termination was legal, the reason it is legal is not because you were in your so-called probationary period, but because an employer in 49 states, including GA, and during the probationary period in the 50th, is entitled to fire an employee for any reason not specifically prohibited by law.
Even if FMLA applied, which it does not because you had not worked for the company long enough, an absence of two days is not sufficient in and of itself to qualify as a "serious health condition" and thus would not be protected. A doctor's note, outside of FMLA, does not provide job protection in any state.
I may not agree with the employer's decision but it is a legal one.