I absolutely did too, and I have a private room as well. It obviously happens, but I do not believe this is the principle.
When I have received the review before the guest actually checked-out (which was not so frequent in my case), the guests’ didn’t have data on their phone (or didn’t have a smartphone), or had late check-outs that was not discussed on an Airbnb conversation.
I have also had cases when I received that email after the guest had landed somewhere outside of Europe (and no data roaming). An 8 hours delay doesn’t make sense.
I have also received those emails 45 minutes after guests checked-out at 6 am to take a plane (but they had data on their smartphone).
I will never know for sure, but I think on the basis of data that I get and try to find a way to explain it.
That is definitely a very special case. Is the review visible on the guest’s profile?