@Rod1399 At this point, I'd say do nothing. How long was their reservation for? If it was just a night or two, you likely don't have a chance to rebook the dates on such short notice anyway. If it was for longer than that, and you think you might be able to rebook the dates if they opened up again, you could message them asking them to officially cancel, as the dates will be blocked, preventing you from taking another booking until they cancel. You could tell them that if you do get another booking for any of the dates, you would refund them for those dates.
Otherwise, since you got paid, just be happy you got paid for people you didn't have to host and who used up few amenities in 4 hours. Hopefully they don't contact airbb demanding a full refund, due to some medical "extenuating circumstance".
As far as the review, just wait on that as well. If they haven't left a review by day 13 and a half after their official check-out time, I wouldn't bother to review. If they do leave a review before then, it will probably be a good idea to submit a brief review, indicating that the guests checked in, stayed a few hours, went out for dinner, then messaged to say they wouldn't be returning due to an unexpected event.(no need to say medical, might be too personal for a public review).
It's weird- I live in the countryside, and most of my guests have been interested in walking around the area, taking a stroll up the arroyo, which has awesome jungle views, etc. But I had some good friends come to stay, they are total city slickers, they went out every day and night, rented a car to see various areas around here, then after 3 days said they'd "done" the town, were bored, and stayed the last few nights until they had to fly back in the city an hour away. They never once even walked the 50 meters from my house down to the arroyo. Just had no interest.