Hire someone or try a long snake stick
Make a long snake stick with some small braided wire and some 3/4" pvc pipe. Glue 3 lengths of pvc pipe together. Drill a small hole for the wire in the end of the pipe, run the wire from outside to inside and tie this end off pull snug. Take the end of the wire on the outside of the pipe and run it down the inside of the pipe making a loop at the top end.Push the loop end up to the top of the mast to loop around the halyard. pull on the free end that runs down the center of the pipe. Tape it off when get the halyard and pull the pipe down. You will need someone to spot the top of the mast, try this on a calm day. I have fished tools out of concrete forms this way before.