@Kesh3 Are you sure that it was a Request, not an Inquiry? As Emiel said, they shouldn't be able to send a booking request for unavailable dates. On Inquiries, guests can enter any dates, even unavailable ones and they have to enter dates to put in an Inquiry. They might do this if they just have some questions, but don't have their travel dates in place yet.
If you are going to be unavailable to respond to guests for 24 hours or more, you can "snooze" your listing. Guests can still see your listing, but won't have the option to book or contact you until you until you unsnooze it.
It's not a good thing for a host to miss that 24 hour hour response window- it will affect your response rate with Airbnb.