No "Hand Brake" on a heavy duty truck. All air brakes. Most likely the adjusters on the air chambers need tightening up, simple maintenance or lack off same. typical in LOS. On the dash of a heavy goods vehicle you have to air valves one for service brakes and one for parking brakes. He probably set the "Parking Brake" but when the individual brake adjusters are not set properly that = no bakes at all, or very little.