The Post and Courier of Charleston reports the animal was left July 9 at the Livestock and Equine Awareness Rescue Network's barn in Meggett.
The man who dropped off the horse brought it in from a local farm. Officials said he left no indication of who he was, worried either he or the horse's owner would get in trouble.
Rescue network director Elizabeth Steed isn't worried about pressing charges and just wants to nurse the horse back to health.
But she says dropping off a horse isn't the same as dropping a kitten at an animal shelter. It will cost $15,000 over four months to care for the horse.