I don't see how your keep could wrap up the chain but I do see how you can wind your chain around a block of mushroom. I did a few times on a shallower mooring than I have now. Shallow water may be more prone to wrapping. In the end, I think you should keep watch of stuff like that, your mooring guy can't be counted on for that. He should give you the right equipment(which varies from locale).Swivels might help but I think you can still wrap your mooring up.

However, your insurance should simply cover any loss or damage. That's what it's for. Still sounds odd though, Doug. Your friends boat wasn't a wing keel, was it?