Boss is angry they need to cover a shift for front desk (I’m not in charge of the front desk)

I have 3 unpaid days that I am allowed to take per calendar year. I used one of those this past Thursday as my flight was changed. One of the front desk staff communicated they were unable to work so the manager now has to cover for them. I am not in charge of the front desk I oversee a different team. How should I respond to this