Messing with serverCmdDropTool isn't the only source of problems, but also the opposite: picking up items. There doesn't appear to be a decent way of explicitly detecting which slot the item went into when picked up other than things like looking at the inventory difference before and after the parent pickup logic. That isn't even necessarily perfectly reliable. Quite a few add-ons mess with item pickup logic to do things like picking up multiple of the same item, changing items on pickup, ammo stuff, etc.