You'll have to pardon the unfinished-ness of this but a while ago I wanted to get down this "missing scene" for a few of the fanart100 promts.

This is when Narcissa and Lucius finally catch up with Draco after they wriggle their way out of the battle.

Just to get you started, in my version Draco was hiding in some back corridor behind a columnm, trying to wait out the fight lol.