According to the article posted on californiadolphin.com:

MALIBU (CBSLA.com)  — Help is needed to find a miniature horse stolen from his secure pen at a Malibu ranch.
Marco Polo, an 18-year-old Liver Chestnut Miniature Gelding, first went missing Saturday and evidence indicated he had been stolen, according to NetPosse.com and Stolen Horse International , which combined make up an organization dedicated to recovering lost, stolen or missing horses.
The mini horse belonged to Barbara Lyons.
“My mother is severely disabled,” Holly Lyons, Barbara Lyons’ daughter, told NetPosse.com. “My mother is extremely distraught and heartbroken that the horse she has owned since he was a baby has been taken from her. She is worried for his safety and welfare and just wants him returned now.”

Marco Polo is 32 inches tall, and has a star-shaped marking on his face. A reward is being offered for his safe return, according to NetPosse.com.

Resource: http://californiadolphin.com/news/109131/miniature-horse-stolen-from-secure-pen-in-malibu