Could this stranger be their older daughter who was kidnapped almost a decade earlier?
A DNA test revealed it was.
On Thursday, the woman who kidnapped the couple's daughter, Zephany Nurse, as an infant from a Cape Town hospital on April 30, 1997, was sentenced to 10 years prison.
Neither the abductor's name, nor the name Zephany grew up with, have been revealed in order to protect the girl's identity.
Kidnapped at birth
Now 19, Zephany was abducted when she was three days old from Groote Schuur Hospital.
The abductor wore clothes similar to the hospital staff uniform, and took Zephany while her mother slept following a cesarean.
Living a lie
The woman raised Zephany as her own child for the next 17 years, never revealing the truth to either her husband or the young girl.
"The irreparable emotional, physical and psychological trauma experienced and still being experienced by biological parents and their [respective] families is unfathomable," prosecutor Evadne Kortje told Western Cape High Court. "The accused has a lack of empathy towards all the victims of the crimes in this matter and she shows a lack of insight in failing to appreciate that she is not the victim in this matter."
A chance friendship
Zephany was raised by her abductor in the same city as her biological parents, and unknowingly became friends with her younger biological sister at school.
Zephany's sister, born four years after the kidnapping, attended the same school and the girls became friends after many people commented on their striking resemblance.
When the Nurses met their younger daughter's new friend, they were so taken by similarities that they contacted the authorities.
A subsequent DNA test confirmed the girl was their missing daughter.
No easy ending
For the Nurses, the mystery of their missing daughter has been solved. But whether it will ultimately prove to be a happy ending will take a little more time.
While Zephany's biological parents have said in interviews over the years that they never lost hope of finding her, for now, the girl remains in the custody of the social services.
The Nurses have been allowed to visit Zephany for short periods, South African media reported.
In March, Zephany herself released a statement
, via the Centre for Child Law, which is representing her.
"I want to say thank you to all the people who supported me through this, for continuously praying and never giving up on looking for me," she said. "Under the circumstances, I am doing fine."