Items will not appear in inventory

[Slanderous]

These are from the vanilla game. It's normal that once picked up they don't appear in your inventory - back in the day FG intended to make various chests that players would open with thalers, and the entities you're using are the remnants of the scrapped mechanic. You either need to create your custom puzzle items basing on the coin bags, or take them from a certain mod, I think it was "Killings in Altstadt". If they're not there, it should be fairly easy to transform them into regular puzzle items though.