I searched for it. The topic is still in twilight. Sun spots have much lower temperatures (3200K) as compared to the normal solar surface temperature (5600K). Some rotational band spectrum have been observed that could be water vapour like. To be sure one has to generate water vapour rotational spectra at suitable temperatures in lab. Experiments beyond 800K are difficult. So there is a possibility but as I said above the area of research seems to be gray in the sense that we have not covered required physical window both theoretically as well as experimentally. And to boot I might be missing some obvious things also - some common question do not have very common answers.