The riders raised the alarm when they came across the car on its roof with Charles Day, 77, still inside.
Mr Day from Sidmouth is believed to have been stuck in his silver Mazda for about six hours after he crashed it into an earth bank. It happened along an isolated dirt track at a location known locally as Tein Pitt Hill at Widden, Newton St Cyres, near Exeter, on Saturday.
Mr Day, from Sidmouth, had been reported missing to the police 12 hours earlier on Friday night, resulting in a widespread search.
He had been spotted on the A30 at 4.30am on Saturday, according to police, but there was no further trace.
At the time of his disappearance, police said they were concerned for his welfare and issued an appeal for information in a bid to trace him.
Mr Day, who also uses his middle name of Raymond, went missing at 11pm on Friday.
At 11am on Saturday, two girls on horses discovered him trapped inside his overturned car which had come to rest against the bank.
Shaken and in a distressed state, he was released from the vehicle within an hour by fire crews who used cutting gear to pull him free. An ambulance paramedic was also on the scene.
Watch commander Ian Treadwell who led the rescue team said: "He was found by two young girls out riding. We were concerned because of his injuries and he complained of pains in his legs.
"It was difficult to get to the car because of the bank. He had been there for some time and the car was on its roof.
"We were keen to release him and we cut away the side of the car pulling him free through the boot.
"Access was also difficult along the dirt track, we had to carry our equipment and gain access from an adjoining field. The track was too narrow for our appliances," he said.
About 15 firefighters from Exeter and Crediton, plus an accident response vehicle from Exmouth attended.
A police spokesman said: "He had left the Sidmouth area in his car and was last seen eastbound on the A30 near Exeter at 4:30am on Saturday.
"Because of the location of the accident, the police helicopter which had been helping in the search was used to take him to hospital."
Mr Day is believed to have been sent home after treatment on Saturday.
May 18, 2010