hugopal maybe.
If he didn’t know it could also be because it’s ‘only’ Alopecia.
If you run in the same circles but haven’t seen each other for ages, and it was something more sinister like Cancer, sure it would spread much more around those circles.
When people like this catch up it can be too brief to get into things like that - people usually stick to the positives and what’s happening (or in their case, occasionally business). The average person will talk about negatives a lot but in these circles and especially where people work together it’s much more generally avoided in favour of being agreeable, positive and building each other up, building good rapport, celebrating successes. It’s how they fuel themselves in a world that is criticising them from armchairs.
If someone turns up to an event like that otherwise looking healthy and laughing at jokes, and just appears to have changed their hair style then I could see how Chris could make a mistake.
We never know what people know, and assumptions are the mother of all fuck ups.