What good is it doing you, to hold onto this sense of offence, JingleMyBells? Is it making you feel good? Happy? I doubt it.
As I said earlier on, we can't control what happens, or what people do or say, but we CAN control our response - and when that response is harming us (and your response is harming only you), we should change that esponse.
Take a deep breath, decide not to let what was said cause you further upset, and then move on.
I am not saying you shouldn't do something about this, if you genuinely believe there is benefit to be gained from challenging what was said, but if you are going to take action, you will do so far more effectively if you are acting with a cool head, rather than from offence and hurt feelings.
I think it was a very common usage of the word, clearly not intended to cause offence - and we are all human, even receptionists and healthcare workers - and it is not reasonable to expect them to censor every single word they say, for fear of causing someone who might overhear, some offence. But, as others have said, it is not a tactful word to use in that context, and a quiet word to point this out to the department, might be appropriate - but only with the aim of asking the staff to avoid using the word 'fit' in casual conversation, not with the aim of getting someone disciplined.