This happens way more times than it just being a one-off 'quirk'. I'm playing Solo and get interdicted, I submit and destroy the offending ship. It drops cargo and/or materials. I lock on to the materials (not interested in the cargo), line up on the floating box and approach it with cargo bay open. Then poof they all just disappear from the scanner. If I'm lucky I can just about manage to grab one before they disappear.