Finance Minister Heng Swee Keat was due to launch a project to promote harmony yesterday morning.
But when organiser Thye Hua Kwan Moral Society learnt that he had suffered a stroke last Thursday, it decided not to invite another guest of honour.
Instead, the voluntary welfare organisation set up a guest book for well-wishers to pen messages to Mr Heng, who remains in stable condition at Tan Tock Seng Hospital.
"We want to show that we respect our guest of honour. It is not right that just because Mr Heng is now unable to come, we get another person to replace him," said Mr Lee Kim Siang, the society's chairman.
"Mr Heng has a very heavy schedule, yet he agreed to come the moment we invited him... He is very good and dedicated," he added.
Mr Lee said the book will be delivered to the Finance Ministry today, together with a miniature model of a roving Harmony Truck launched at the event at the Singapore Flyer.
The actual truck contains information about the culture and beliefs of the different groups in Singapore, stories of new citizens and foreigners, as well as the racial riots here in the 1960s, and is part of an ongoing effort by the society to educate the public about the importance of racial, religious and social harmony.
It will travel to parks and foreign worker dormitories, among others.
The truck will also be at Bishan- Ang Mo Kio Park on June 19 for a family breakfast event featuring food from different local cultures. On June 25, it will be at the Youth Park in Somerset for a supper event to reach out to young people and help them understand the importance of racial and religious harmony.
Yesterday, Mr Lee also led more than 300 guests at the event in a silent prayer for Mr Heng's recovery.
In the guest book, he wished Mr Heng a full and speedy recovery, while Sinda chief executive Kumaran Barathan wrote: "Have a speedy recovery. God bless."
Separately, Communications and Information Minister Yaacob Ibrahim told reporters at a Mendaki event on education issues that Mr Heng is under constant observation.
"We need to give space to the family but, most importantly, let us continue to pray for his recovery because he's a very important part of the Cabinet. He's a very important part of our Government in charting the future for Singapore," he said.
Home Affairs and Law Minister K. Shanmugam told reporters at a HomeTeamNS run that he was also struck by the professionalism of the Singapore Civil Defence Force (SCDF) team that attended to Mr Heng when he collapsed in the Istana's Cabinet room last week.
Prime Minister Lee Hsien Loong had, on Saturday, written to SCDF Commissioner Eric Yap to commend the four officers involved.
Mr Shanmugam said yesterday: "We were standing in the room, PM was there, senior ministers were there, the entire Cabinet was there.
"The SCDF officers - very young people, led by a lady - came in. They ignored all of us, they focused immediately on the patient and it told me that they were professional, they have been well-trained.
"It didn't matter who the patient was. In fact, they didn't know who the patient was until they came in."
Mr Shanmugam noted that the officers even questioned Minister of State Janil Puthucheary, a trained paediatrician, who was already helping to resuscitate Mr Heng, because they felt what he did was different from what they had been taught.
"He said it was right of them to question him. He then explained to them why he was doing it differently because of the circumstances," Mr Shanmugam added.
"Certainly, they didn't show any signs of any additional pressure. That is testimony to the professionalism and the training that the SCDF officers get," he said.
• Additional reporting by Amelia Teng and Yeo Sam Jo