Ramp personnel reported the aircraft rolled after disconnecting the towbar. The pilots did not respond to ramp personnel attempts to signal the pilots to apply brakes until the reporter tapped on the aircraft fuselage.

Narrative

On that date we were working flight ABCD. The following statement is to the best of my recollection and after reviewing the video. The incident occurred a week ago; when we pushed out the flight and disconnected the tow bar; from the aircraft. I was on the right wing and was tasked with the actual disconnection of the tow bar. Person A was the driver and was on the headset in communication with the pilot. Person B was on the left wing and was tasked with notifying the pilot when all was clear. Person A pushed out the aircraft to the alley and came to a stop. Once he was stopped I walked over to the tow bar and began lowering the landing gear on the tow bar but leaving the wheels off the ground about an inch or so. I leave the wheels off the ground so that I don't create tension and/or possibly to cause damage to the equipment or aircraft in case of any movement. Once I lowered the wheels I looked and Person A to give me the brakes set signal. I then returned signal. I then proceed to disconnect the headset cord and the towbar. Right before I lift the handle to release the tow bar I normally look at the light and see if it is on. Meaning the brakes have been set. I am not 100 percent sure as this happened a week ago. I do remember lifting the handle and seeing the tow bar dropping to the latch that holds the tow bar in place. After the drop Person A reversed about a foot and stopped I noticed the plane start to roll forward. I motioned to Person A to move out of the way to reverse as the plane was moving towards the push out tractor and tow bar. He did reverse about 10 ft and stopped. I signaled to Person B to notify the pilot so set brakes to which he did. Seeing the plane was not stopping I signaled to Person A to move out of the way and clear the area as to not create any damage or possibly get injured. Person B was furiously trying to get the pilot's attention; but the pilot was not paying attention to the situation. Person B was even jumping up and down waving his wands. I noticed Person A was clear and out of the way and since the pilot was not responding to Person B I then carefully without getting ran over by the plane I tapped the fuselage and then a few seconds and about 20ft later the plane came to a stop. I then proceeded to disconnect the bypass pin and walk it over to Person B. Person B showed the pin and I believe saluted him. I then proceeded to calm Person B down as we were lucky that our quick thinking adverted a possible aircraft damage or worse possibility of an injury to a passenger; flight crew or coworker.I'm not sure why it happened. Person A said that he gave the command to set brakes and pilot said they were set. I do know that after the event it seemed the pilot was distracted. Maybe he accidentally released the brakes. The reason I say he was distracted was because Person B was trying to get his attention and he did not react or responded by setting the brakes right away. It wasn't til I believe I tapped on the fuselage that he reacted.As mentioned above. I quickly motioned for Person A to move out of the way. And signaled for Person B to get the pilot to set brakes. I believe after I tapped on the plane is when he realized what was going on. Once he set them. He did not call to return to gate or anything. Nor did he call ops. He taxi out and left.Suggestions: Honestly; I guess double confirmation on brakes being set from push back operator and pilot. Also while disconnecting tow bar pilots have to remain aware of ground crew and not distracted.