Did the same thing to me.
Had a P/U appointment in Ohio for 5:00 PM. Our Customer Service called at 3:00 PM to be sure they were on line. She was told that the driver was already there and waiting to be loaded.
We called the following morning to check on delivery... "Oh the driver wouldn't stay... he came home on his own."
I'd say that they found something that paid more or a direct customer called with a load close by and they jumped on ours.
Be careful...