The three-month-old colt was found in Braintree, Essex, earlier this month (10 July).
He had suffered other injuries that the RSPCA believes to have been caused by a hit and run vehicle incident.
A member of the public found Murphy, as the youngster is now known, and put him in a nearby horsebox and kept him safe until the RSPCA arrived.
“Poor Murphy was in a sorry state when I arrived to collect him,” said RSPCA inspector Sam Garvey.
“Not only was he suffering with suspected hit and run injuries, he also had very nasty burns to his face and body. We do not know exactly what caused these burns — but we think it was some external cause.”
Murphy was taken Catley Cross Veterinary Clinic in Halstead, Essex, where he received treatment for his burns and injuries.
He will be moved to RSPCA Millbrook, a specialist equine centre next week where he will continue to be cared for.
“So far no owner has come forward and we are urgently seeking information about Murphy’s mum, who is no doubt extremely stressed to be without her foal,” added inspector Garvey.
“It is not yet known who owns Murphy, as well as who was driving the vehicle that hit him, and who inflicted the burns,”
Anyone with further information about this incident can call the RSPCA inspector appeal line in confidence on 0300 123 8018.