I wanted to note that @Dielos was right about registering the filters. There is a note in the Differences between Skyrim and Fallout 4 in the creation kit notes that mentions this fact. It is obscure and caused me more than a bit of grief. A number of great tutorial videos show them using the event without a filter so it was confusing. Here is the link: OnItemAdded and OnItemRemoved no longer sent without filter
Event OnInit()
AddInventoryEventFilter(pma_Railroad_ClothingArmor)
AddInventoryEventFilter(pObjectTypeArmor)
EndEventYou need to set the filter to a Form, Keyword, FormList, etc. that you want to match.