Idowu, silver medallist at the 2008 Beijing Olympics, is one of Britain's top medal hopes for this year's Games which start on July 27.
He had been expected to face world champion Christian Taylor of the United States at the Diamond League meeting but his late withdrawal was announced to the packed Crystal Palace stadium about 20 minutes before the triple jump competition was due to start.
It was embarrassing for organisers and worrying for British fans, but Idowu - who is renowned for his cautious behaviour leading up to major tournaments - allayed fears by saying the move was precautionary.
"Sorry to have to pull out, slight bit of muscle tightness. I will be fine in a day or two," the Londoner said on Twitter.
Hurdler Tiffany Porter also pulled out with an injury but, despite breaking down in tears afterwards, she also said it was a minor problem.
Sayers, meanwhile, unleashed a British record 66.17 metres to beat world record holder Barbora Spotakova and give her Olympic credentials a major boost.
Sayers was fourth in Beijing four years ago and also just missed out on the podium at the recent European Championship in Helsinki and her first round effort moves her to fourth in the current world rankings.
Olympic champion Ohuruogu beat world champion Amantle Montsho in a strong women's 400m field, the Londoner coming home in 50.42 in terrible storm-like conditions. Rosemarie Whyte of Jamaica was third with Britain's Shana Cox back in seventh.
It was in stark contrast to Ohuruogu's 'appalling' performance - as the Olympic champion described it at the time - for last place at this meeting in 2011.
"I've done all the work so I'm happy that I can take something like that away. I knew I had a good chance, I saw her (Montsho) look back so then I thought, 'I've got you now'," said Ohuruogu, who was disqualified from the world championships last year for a false start.
Elsewhere, Great Britain's Yamile Aldama finished third in the women's triple jump, which was won by Colombia's Catherine Ibarguen, while European champion Robbie Grabarz settled for second in a high jump competition claimed by Canada's Derek Drouin.
Andrew Osagie placed third in a high-class 800m won by Poland's Adam Kszczot while Daniel Talbot, not selected for the individual 200m at the Olympics, finished third ahead of both Christian Malcolm and James Ellington, who were chosen.
And Great Britain's Nigel Levine, Martyn Rooney and Conrad Williams finished fourth, sixth and eighth in the 400m, which was won by Grenada's James Kirani.