Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Communication Breakdown; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Object
Flight Crew Returned To Gate; General Maintenance Action
Human Factors; Procedure
We were pushing back; communications were established and ops were normal.  We had been cleared to start and had started the number 2 engine. At one point the pushback stopped; a bit sooner than I expected. I assumed there must be something blocking our path. After a short delay and not hearing from the tug driver I tried numerous times to contact the driver. I got no response from him. I noticed the aircraft moving forward; leaned forward to see that the tug was not moving (not towing us) and went for the brakes. However; it was too late and I felt a small impact. I set the brakes. I opened the flight deck window and attempted to talk to the ground crew. Communication was difficult. There seemed to be a language barrier and the tug driver's headset was malfunctioning. I think it might have been a Bluetooth headset. After several minutes of trying I was finally able to talk to the driver on the headset. I told him that we struck something. I told the driver that we would need to be towed back to the gate for a maintenance inspection. I thought I was quite clear. Instead the driver disconnected the headset and drove away. The marshaller attempted to give me a salute as I was shaking my head 'no.' I did not flash my light to accept the salute but the marshaller just walked away. I had the First Officer shut down the number 2 engine and inform the ramp tower that we needed a tow back to the gate for maintenance inspection. It took quite some time to get another crew out there. In the mean time we called maintenance and I entered the need for an inspection in the Log. No damage was found; the inspection was signed off and we departed again. Failure of the tug driver to follow standard operating procedures after a failure of the tug driver's headset. No attempt was made to substitute hand signals after a failure of the headset to assure brakes were set. Emphasize the importance of standard operating procedures to ground crews.
B737 Captain reported the aircraft rolled forward after push back and a small bump was felt before the brakes could be set. The ground crew attempted to release the aircraft over the Captain's request for maintenance inspection.