I think it can be iffy to ask if someone is ok after one or two days out where my own work is concerned. If a person is out 3 or more days, that's personally when I raise my own eyebrows since by virtue of contract that's doctor's note territory and the person is most likely been really really sick. Using up some sick days isn't totally uncommon for many. And it can be fast paced at work that days blur together. So there's that angle as well. Sick days can often be a don't ask, don't tell scenario in my experience.