@Jason-P2 . Were you able to contact the booker at all and if so, what did they say? I have not had this happen to me but I am heavy on the communication with guests leading up to their arrival. Non response would be a flag for me to pick up the phone usually.
I would wait until closer to the 14 day expiry following the check out date and time, in case the guest submits a request for a refund, you are contacted by Airbnb, etc.
If still nothing, you can simply say guest did not arrive and if they didnt communicate anything mark them down in that area. Use something else area to leave notes With more of the AIrbnb system running on AI these things will potentially happen.
Hope this helps.