You can file a grade grievance if you wanted, but I’m not sure that would get you far. Most courses have a policy that if you decide to show up to an exam at the normal time, even if you were sick, then they will not factor in the fact that you were sick. So I think you are most likely out of luck there.
Also, if you are allowed to miss a certain number of classes without penalty (i.e., they drop your lowest X attendance scores), that isn’t an invitation to just blow them off. Usually they should be reserved for if you are actually sick or have some other legit issue. When I was a GSI before, my policy was that if you needed an additional dropped score, then you had to be able to provide a documented excuse for all of the default drops, plus the additional one. If you are very near a grade border or if you are borderline pass/fail, and they say they will look to see if there is justification to bump you up in those situations, then they are looking for extra effort. Just because you did the minimum to get full points does not constitute sufficient justification.