My Alfa 159 went to my local Alfa dealer/garage for an MOT, service and clutch replacement. According garage, after doing this work the engine was running, then suddenly there was a loud rattle from the top of the cylinder head. The engine was stopped and the cambelt covers removed - the engine would not turn over fully as something was restricting the rotation of the crankshaft. Apparently, the valve timing was out and the water pump has excessive play. They inspected the valve rockers – all ok, then removed the cylinder head and found a small piece of metal in the cylinder. They then inspected the intake manifold to find that of the 4 metal butterflies that should be in the manifold, there was only one left - the remaining butterflies have broken up and gone into the engine. Is there any explanation for this, or was the garage negligent?