The 24-year-old maritime studies student was last seen on August 1 at about 6.50pm wearing a jersey with thick pink-and-white stripes, black skinny jeans, a cream beanie and white Superga takkies.
Her family say her bank card was used at the Golden Acre and R300 was withdrawn the following day.
She left a note reading, “Start your search in Camps Bay if I am missing for more than 21 days”, in her room at the Catsville Residence.
Her older sister, Lazola, said she had assumed Sinaye was in class or busy studying for exams when she couldn’t get hold of her on the phone on the morning and night of her disappearance.
The note was found by someone who is in charge of the residence after Lazola had called and reported she was worried that she couldn’t get hold of Sinaye.
CPUT management and police have asked anyone with information about her whereabouts to contact a student affairs development officer or to report it to Woodstock police station at 021 442 3117.
Meanwhile, a Bonteheuwel family has appealed to the public for help in searching for missing Dunane Clarke, 34.
They said they were running out of options as they have called hospitals and morgues.
Her sister, Rizaan Tiffloen, said the mother of three had last been seen last Friday when she said she had to quickly go to the bank at about 3.30pm, but she had never returned.
“At the time she was wearing blue jeans and a white T-shirt. She has never just disappeared before hence my mother got worried when she didn’t come back and it was getting late.
“When I tried calling at around 6pm, her phone went straight to voicemail. We have made everyone aware that we are looking for her. We have also reported her missing to police,” said Tiffloen.
Bonteheuwel ward councillor Angus McKenzie said: “We are all involved in the search operation, Neighbourhood Watch and various other community-based organisations. We all want her back home soon, safe and unharmed.”
Anyone with information can anonymously contact Crime Stop at 086 001 0111 or SMS Crime Line at 32211.