Hi Nathan,
well you do find yourself in a interesting quandry with this one for sure, I am sure that the bride and groom were only too pleased to have such an excellent photographer stand in at the last minute. Now as for the copyright? I don't practice law but you as I see it were the "Artist" using someone else's equipment, the camera you used belonged to someone who was either new to photography or was new to the equipment so I doubt very much that they would be able to match your excellent quality of work. In my heart I would say the images were yours, in law I would say they belonged to the person who owned the camera. Morally the couple who's wedding it was would be the most to benefit from the photographs, not an easy one mate, would be interested to find out how this one is resolved.
What are your feelings on the subject? were you happy to be able to just make their day for them as that's how I would feel for sure. Good luck with this one
David