Teo Lai Huat, 54, came across the diamond solitaire near the rear door of his bus while carrying out a routine inspection at the end of his shift at Kent Ridge Terminal, SBS Transit said in a Facebook post on May 25. He performs the same sweep after every journey to make sure nothing has been left behind, he said in the post.

The ring belonged to Clarissa Tan, who said she lost it on SBS Transit bus service 10 at around 10 p.m. on May 11, while travelling from Siglap to East Coast Road after drinks with friends, according to a Forum letter she wrote to The Straits Times. She realized it was missing only the next morning.

"When I contacted SBS Transit the next morning, I was told, to my relief and gratitude, that Mr Teo had found the ring at the end of his shift at Kent Ridge Terminal and dutifully handed it to the office," she wrote.

In response to queries from The Straits Times, SBS Transit said Teo had grasped at once how much the ring was likely to mean to its owner.

"Realizing that the owner would likely be deeply distressed over the loss of such a valuable item, Lai Huat immediately handed the ring to his supervisor at the terminal so that it could be safely kept in case the owner returned to look for it," the operator said.