An unidentified air carrier aircraft came loose from the tug during pushback when the pushback crew secured the tow bar to the tug; but not to the aircraft.

Narrative

When we called for push the Ground Supervisor told us that we had to hold for five minutes. We acknowledged and waited the 5 minutes; during which time the Supervisor and tug driver sat next to the tug talking. They got in tug when we again called for push. This is when they realized that they hadn't hooked up the tow bar during that five minute sit. The tug driver seemed to have trouble getting the tow bar attached to the tug. After another 3 minutes during which the Supervisor did not assist him in attaching the tow bar he finally had it hooked up and we were ready to go. We started the push and the aircraft came loose from the tow bar. The driver had spent all his time hooking the bar to the tug and hadn't checked the connection to the airplane. After the tow bar came loose the plane continued to roll back on its own. We recognized it immediately and the Captain told me to tell the Flight Attendant to brace. I hit the emergency call and before I was able to talk to her the plane came to a stop about 20 FT from the release point. The plane had come to a stop before we needed to pull the parking brake; however the headset chord had pulled to the point that it broke and we decided it would be best to have Maintenance take a look at the airplane and make sure there was no damage. We started up and taxied back into the gate for the inspection. They found no damage.