I lost the entire halyard and tied up next to a boat with a taller mast. Winched the two boats towards each other and went up the mast on the other boat. Then fished a messenger line and weights over the sheave to get the new halyard run.
You won't have to go to that extreme, but if Mark ever gets Nemesis splashed, maybe you could go up the mast on Nemesis and reach over to grab your halyard!