If this happens, I would recommend looking into whether there were certain times where he lost something and didn't get angry, and if so why, or looking into why he's losing items. What are the shared features of the lost items? Behavior change usually doesn't occur by directly targeting the thing you want to change, but by indirectly targeting the behavior; by looking at how and why the alternatives occur. That is what you were doing with counseling another way to react to the situation. If the behavior could change by directly targeting the behavior, the problem likely never would have become prevalent enough to come to your attention.