Is this a bug or intended? I am able to craft items without actually having the item.

For example. To craft the rubicon mask I need 2 plastic pieces. I picked these up and applied them to my crafting screen. I then realized I needed a screw to finish the mask and placed the plastic down on the ground. Walking about 40 feet away from the plastic I found some metal and my screw and was still able to use the plastic I placed in the craft window although it was not on my person.