I am trying to retrieve items, but the client I am working with set up their preexisting system such that the items I am trying to fetch are not in the catalog. The catalog only has items available in their online store, and I am working with items that they only sell at a physical location. If I go to the dashboard → items library I can find them, but listing catalog using the api explorer does not include them. I need to retrieve their item IDs so that I can create an order with those items. How do I do this with the square API?
All items in the sellers Catalog are returned with the API. Are you paginating through all the catalog objects? 
Thanks, that was it.