Hi Bob
Glad you were safe!
Had the topping lift shackle do the same thing this past summer in very heavy conditions while heading to Boston from Kittery, ME. Noticed the block/lines flopping around near the aft end of the boom.
When we got into the outer Boston Harbor we slowly lowered the sail into the stackpack while making sure we were directly into the wind allowing the sail to lay on the dodger and bimini. A piece of the shackle was still attached, looking the same as your shackle photo. Put a new shackle in place and was able to properly lift the aft end of the boom to prevent damage to the bimini during the hour long trek to Constitution Marina.
Peter Grabow