@Michelle-And-Steve0
I would not worry too much about this issue. With a serious illness they can most likely claim from their travel insurance.
In any case, you do not really have any funds to refund until you have the payout, so I suggest you wait till your payout is there in order to determine if there is anything to refund at all.
If the refund button has disappeared, there is also the possibility that airbnb has refunded them in full under the extenuating circumstances clause. Another reason to wait until payout day.