Ice... I bet I know what happened with yours...

From other pictures, your leash on the bungee looked to go through only the arch on the shelf bracket. I'll bet when the SUCKgate came loose, it just ripped the weld of the arch off and came undone that way because of all the water pressure/resistance when that bungee hit its max extension. I put my leash around the handle and the lower shelf supports that were bolted to the HOD. You can kind of see that in my picture sitting on the back of my boat.

This is all assuming you didn't lose the bungee tie. If your bungee cord came off the boat entirely, then I'm totally off base here haha.