Satellite Parking,
Sorry to hear about your experience with AA. I agree that even if AA had to pull some agents to help get the next flight off, they should have left at least one agent to process the existing line.
Go to AA.com, click on "Contact Us" on thetop right-hand side, then select "Customer Relations", to send your complaint. I'll caution you that this is just a place to start. There is no telling when or what kind of response you will get. But don't give up, you have a valid complaint. Also, the art of complaining can play a factor in how good a response you might get.