Even during the winter months we're excited about humidity being below 60% and don't think a thing about 90%. (Some do complain when it goes higher than 90% though, but those folks have trouble making words when it is 100% so it all comes out OK in the end.) We just went through the biggest flood in recorded history here too. There have been no cases reported of mold in the lungs. So 90-100% humidity and mold everywhere and it isn't growing in the lungs of folks here.
I'd suspect that vapers would be even less likely to have this odd occurrence. That water that makes vapor so visible is coming from our insides. Which is why the constant advise of drink more water is so often heard. Vapers need to replace the water the vapor is drawing out of them. Seems vapers, as a group, would have the least likely place to have lungs suitable for mold growth.
I'll leave out that someone would have to have some serious existing lung problems to even make mold growth in the lungs even possible...