It was their first time sending their pet chihuahua to Pet Lovers Centre (PLC) for its monthly grooming.
Ms Aileen Tung, 46, and her sister, Jess, 34, stood outside the glass window of the room where the grooming was being carried out and watched four-year-old Lilo's coat being shaved.
Then they suddenly noticed panicked expressions on the faces of the groomer and his assistant. The assistant took the dog to a basin and both groomers started whispering to each other.
Ms Tung told The New Paper: "At that point, our hearts sank as we knew that something had gone wrong." The sisters rushed inside the room and were told by the assistant that their dog had had a small piece of flesh torn away from one of its ears.
Ms Tung said: "The main groomer stood quietly as the assistant told us about the accident. He did not explain how it happened at all and just advised us to bring Lilo to a vet immediately."
At the veterinary clinic, Ms Tung was told that her dog could have its ear stitched back.
However, she claimed the groomers had thrown away the torn piece of flesh.
The incident happened last Friday at Kensington Park's PLC branch.
Treating Lilo's injury cost about $270.
Ms Tung said that when she asked about the assistant groomer's qualifications, she was told that he did not have any.
PLC spokesman Loh Mun Loong confirmed that the employee who handled Ms Tung's dog is an assistant groomer who is not allowed under company rules to carry out any cutting or shaving.
"Failure to comply with this protocol amounts to misconduct," Mr Loh stressed.
He added that the assistant groomer is no longer serving at the grooming centre. PLC has also reminded its groomers about the rules and its "zero-tolerance" policy for non-compliance.
Mr Loh said PLC's chief executive, Mr David Ng, has personally apologised to Ms Tung.