I would think that this isn't a case of your account being hacked... b/c if someone was going to hack into your account and steal your points, they certainly wouldn't make an award reservation in your name (!), but would probably change the address and then redeem points for something like a gift card.
Being that you have a revenue reservation at the same property for the same day, I would guess that perhaps someone at the hotel somehow screwed up your reservation and accidentally made a duplicate reservation using points.
Thanks - that seems to fit the facts, as you say not exactly hacking behaviour !
I need to contact MR about another matter, I will ask them if they can tell who may the redemption booking and how.