had the same thing happened to me went out to work found m back bumper damaged, a silver piccaso was also damaged in roughly the same area to where it would of hit but it was also damaged in 2 other areas so they could easily blag it was already their.
a women hit my mums focus and did quite abit of damage like in this post she drove off and parked the other side of the car park,luckily my gf was in the car park at the time and saw her and knew it was my mums car (pretty lucky tbh)
my advice is take pictures of the nissan get in contact with the police, that way when the police go to their door step their more likely to feel the need to own up to it