@Mish1
Mish, it may never happen to you again but, just remember you never, but never cancel a confirmed guest reservation!
If a problen arrises that prevents you from carrying through with a hosting get onto Airbnb first and explain your extenuating circumstance.....Of course you had a good one, but not an automatic one!
When you contact Airbnb they will endeavour to relocate the guest or refund them but, this must happen after discussion with Airbnb! If you hit that cancel tab you will suffer the consequences I am afraid.
It seems that Airbnb are becoming slightly more concilatory where host cancellations are concerned but, it's not up to you to decide if it is fair or not, it's up to Airbnb!
Cheers.....Rob