Use the CTRL A then CTRL C option. I do that sometimes to keep from losing posts. Also CTRL Z can get you back sometimes. I lose stuff that I type because the mouse on my laptop is positioned wierd and I erase all that I have typed by accident.
Probably your computer or internet provider. If...
It happens often and is par for the course. People just flake out. It's frustrating, but what ya goin' do???? I would relist it now. If you sell it then it's his loss. He should have maintained communication.