Find an item in the world, select it, and call in Ewan. As Ewan is coming out to get the item, run, or even better yet, drive away. You do not have to go too far; just until it is no longer on your mini-map. If done correctly, you should see a message reading "No Resource To Pick Up", and have said item added to your stockpile. This works for money, munitions or fuel.
