I think that John is correct. It was a Taxi driver most likely. If he took longer to cancel you could accept, and then click on pick up rider, start trip. Then drive to Miami!!! LOLI kept my App on last night as I stay up late. It was so dead I was the only Uber of any kind anywhere near PBX or downtown. About 1AM I get a ping from the airport. I accept. I'm 7 minutes away. In 10 seconds the rider cancels. No problem, maybe there was a taxi available, although I suspect a delayed flight and no taxis around.
2 minutes pass and same guy pings me back. I accept and IMMEDIATELY (1 second) he cancels again. A few minutes pass and a different guy pings me from PBI. I accept and IMMEDIATELY (1 second again) it's canceled. In the course of the next 15 minutes this 2nd guy pings me 5 times. I accept all of them,. Most are canceled in 1 second but one time I had time to call. No answer.
So I emailed Uber CS and asked them if their system was working properly. It seems a but unlikely that somebody would be playing around with the Rider app at the airport at 1AM, and there were 2 different ones doing it. Uber CS replied with a form letter telling me that they canceled in less than 5 minutes and therefore I wasn't allowed a cancel fee. I emailed them back and told them I was not looking for money and to please read their emails before sending out form replies. They haven't responded.
I find it weird that the ride could be cancelled within 1 second of when I accepted it so many times. If the rider pings me and then cancels while waiting for me to accept it or not, do you think the Partner App is programmed to wait and see if I accept or not before it actually cancels me out? That's what I suspect.