If you locate a container, you can scan its contents by getting very close to it (with the nose of your ships facing the container), then activating the tractor beam, the container's stored contents will then be displayed on your Heads-Up-Display. If you let the tractor beam reach full power, one item of the container's contents will be transported to your ship
Altho it talkes about containers. It definitely does not work for me on the leftover stuff . I guess it's only the containers lying around? I don't remember but I'll go and double check.
I don't know where you found that piece of info, but it's news to me. In order to "see" what's in a container left by enemies, you must also have a "cargo scanner".
Never heard of it being done any other way.
Good Luck...
\"To kill hubris with humility is a goal rarely achieved by men\"