The item in question is mostly likely a Recipe.
Recipes give players the ability to create the respective item in the Recipe. To craft the item, all they need is the necessary materials the Recipe requests. Since a Recipe is not the actual item, it is not stored in a player’s Inventory.
A player can see their Recipes at the Craftsman Ship in the Marketplace, and can also craft Recipe items there.
For more information on Recipes, please see the article below: