Gary and Amigo on their first ride since Amigo's injury.
It has been a remarkable journey for Amigo, who overcame a series of life-threatening problems during his recovery, watched by a growing legion of fans on Facebook.
Amigo handled the ride well and the pair have since been out again.
Gary told Horsetalk that Amigo's vet bills amounted to $US35,000. He said that an anonymous donor who gave $US11,600 towards Amigo's care continued to meet the vet bills as the costs climbed well beyond his means.
The accomplished endurance horse accidentally impaled himself on a large branch in his paddock in mid-January.
The branch broke two ribs and penetrated his chest cavity. Amigo was seriously ill when taken that day to the the Large Animal Clinic at the University of Tennessee.
The 90-centimetre stick was removed in an operation - all performed with Amigo standing up - but he was given only a 2 per cent chance of survival.
He defied the odds again and again, overcoming, among other things, the threat of laminitis and serious infections.
During a follow-up standing operation to clear a stubborn access, Amigo was nearly lost when both his lungs collapsed and he went down. Veterinary staff revived him and Amigo slowly but surely bounced back.
Gary obtained a credit card dedicated to animal care and was able to max that out with $US10,000, repayable over a period of up to 60 months at an interest rate of 14 per cent.
Gary, who works in the health and safety field, took an extra part-time job in a home improvement store to help meet the mounting bills.
Fans on Facebook rallied to raise money and more cash came in through sales of Amigo merchandise - T-shirts, tote-bags and mugs.
However, it was an anonymous donor who really turned the tide, with their contribution of $US11,600.
The money went to the university clinic, but the costs continued to climb.
Gary recalled how, as the debts mounted, he told the large animal clinic that he would have no choice but to take Amigo home early.
Amigo, however, was able to stay put. It transpired the anonymous donor had been checking every three or four days about the cost of Amigo's care and kept paying the bill.
"It was amazing," said Gary. "It floored me. I never knew people had that kind of heart.
"Even if I did know who it was, what would I tell them?"
Gary said he wrote a three-page letter to the benefactor, which was passed on through the university.
"I don't know how you would ever repay someone like that. I sure do appreciate it. That donor and the fans on Facebook sure saved my tail!"
Amigo came home in mid-April, still with a gaping wound in his side.
Gary had to clean the wound twice daily and tried doing it with a turkey baster with limited success.
The clinic suggested a weed sprayer and Gary never looked back. He had to stand Amigo on an old tarpaulin to collect the infective material washed from the wound, which at that stage still penetrated into the chest cavity.
"It started to heal up really quickly," Gary explained.
With the wound all but closed, Amigo underwent a small procedure to open the injury more to allow it to continue to drain.
A check-up back at the clinic in May identified a growing pocket of infection. The clinic tested a sample and identified the streptococcal strain responsible.
Amigo then went home and on to a specially formulated antibiotic cocktail to attack the infection.
Gary said the open wound behaved much like a blowhole. At times when Amigo was grazing it almost seemed like he was breathing through the hole in his side and not his nostrils, Gary said.
The wound has since sealed over and Amigo is no longer on antibiotics.
Amigo passed his most recent check-up 12 days ago and was cleared for light riding.
Gary saddled him up and, in honour of the efforts of the university's large animal clinic, rode him in an orange halter - the university colour.
Amigo has stood up well to his two rides, but can still be worked only at a walk. Gary said the horse still has only 25 per cent function in his left lung and about 95 per cent in the right.
It was hoped Amigo's lung function would continue to improve.
Gary says he is now fine-tuning a book he wrote about Amigo's recovery, which runs to 15 chapters and about 149 pages. He began it in March after being prompted by Amigo's Facebook fans, who today number nearly 10,000.
Gary said he was uncertain whether Amigo would one day make it back on to the endurance circuit.
"Only time will tell. He has surprised me so many times."
Gary said both he and Amigo's veterinarian, Dr Nick Franks, had seen Amigo defy the odds time and time again. Neither was now prepared to place any limits on how far Amigo's recovery would go.
At this stage, Gary is aiming to take Amigo on a trail ride in September.
Gary said he had been able to give up his part-time second job, with his credit-card bill now standing at around $US1500. Every cent he earned on the second job had gone to Amigo's care.
Gary can now reflect on a remarkable journey that has had a happy ending.
One legacy is a fund set up in Amigo's name at the university to help take the financial burden off someone else who one day has a sport horse with critical injuries.
The case attracted international attention and thousands of Facebook fans still share in the daily miracle that is Amigo.
As for Amigo, he spends the hot days of a Tennessee summer in his stable and ventures out with his buddies at night.
He is happy, contented, and enjoying the trappings of life with Gary in Luttrell. That's just the way his fans would want it.