A: Magic Ring? What Magic Ring? I don’t see any Keepers there at all!

Once you have “put on” the Ring by picking it up off the table and putting it back into your hand (facing out) all of your Keepers are “invisible” and cannot be interacted with.

But, more to the point, the Magic Ring is no longer in play (face up on the table). It’s in your hand. This means that, while one can’t use Steal a Keeper or Exchange Keepers to get it, note that someone could get it by Trading Hands with you.