Often times the owners will be searching for a missing pet for months. It would be good to go back and see if it has a collar. If it does it is right to call the owners and let them know what happened and where to find the body.
This will be very difficult but will provide the closure the mourning owners need.
Many pets are also equipped with a microchip and if taken to an animal shelter/the pound they can scan it and find out who it belongs to in order to notify the family.
Cats are as important as children to some people(including me) so consider that when thinking about this. And think about the fact that it may have come from a family with children.
Legally, you are fine. It was an accident. If you are truly sorry, just take the small amount of time to clear your conscience.