Spawn Explosive specialist in editor
go to inventory and drop backpack on the ground
walk few metres away
drop vest on the ground
walk few meters
drop uniform on the ground
walk few metres
drop weapon on the ground

Open debug console and add event handler:

player addeventhandler ["take", {hint str _this}];

Now turn around and point at weapon, you should see "hand" use default action to pick weapon up. event fires
Go to uniform and do the same. event fires
Go to vest and do the same. event fires
Go to backpack and do the same. event doesn't fire.