Two employees were assessing the source of a thumping noise on an unloader machine. The injured employee was lying down on the floor, parallel to the unloader machine, using his flashlight to look into the bottom of the machine. He reached up with his right hand to identify a vibration or temperature when his hand got caught in a pinch point between a roller and the drum/drive, resulting in a laceration to the palm. The machine was not locked out or tagged out at the time of the incident.