Originally Posted by Worhammer
As he said, you come up to them in scan mode and it should pop up. If you press the back button, it'll show red if you've collected it. It should also pop up and say "Scrap Collection A" or B or whatever.
also if you have the part (preorder DLC versions of the weapons don't count) it won't be awarded to you but you still get the credit for picking them up.