Although the culprits have never been officially identified, it was widely speculated that the IRA was behind the kidnapping. The group has never officially claimed responsibility for stealing the horse.
"This is really the Shergar story of the greyhound industry," a high profile greyhound trainer told the Limerick Leader newspaper.
The theft was discovered after his kennel was found empty by a kennelhand on Monday morning.
Mr Holland and wife Nicky had reportedly gone away for the weekend, and were on their way home when the dog was discovered missing.
There have as yet been no leads as to the greyhound's whereabouts.
According to the Racing Post, the Holland family are believed to be 'very distressed' by the theft, and Mr Holland spoke briefly only to say: "We have no news as yet."
Clares Rocket is widely regarded as one of the fastest and best greyhounds to have raced in years, and was a favourite the 2017 English Derby.
The Gardai press office in Dublin confirmed the theft was under investigation.
"Gardai are investigating the theft of a dog in Golden, Tipperary," a spokesman said.
"The theft is believed to have happened at some time between 6pm on December 4 and 10am on December 5. Gardai are appealing for witnesses."
The Irish Greyhound Board declined to comment on the matter, with Chairman Phil Meaney saying only: "It is now being dealt with by the Garda authorities and it is out of our hands for the moment."