The sources did not say where she had gone.
Thailand's junta chief on Friday ordered border checkpoints to be beefed-up after Shinawatra failed to turn up at the court.
A Supreme Court judge has postponed the verdict to September 27.
Ms Yingluck denies any wrongdoing, saying that she did not oversee the scheme's day-to-day operations and that it had contributed to the country's economic development.
The sources did not give details of her current whereabouts.
"We have heard from officials that she hasn't showed up", Deputy Prime Minister Prawit Wongsuwan told reporters, according to Reuters. The court said Yingluck, who had pleaded not guilty in the case focused on a rice subsidy scheme for farmers, had told the court she could not attend as she was suffering from an ear problem.
"We think that the defendant is hiding or has fled", a statement from a Supreme Court judge said.
Yingluck could prove the second Shinawatra to evade a verdict in a corruption trial. "She asked for sick leave not to show up today".
Yingluck said at the time of her overthrow said she had acted with integrity and honesty during her time in power. The government was nervous about their reaction.
"What they thought (about) was only the beneficial impact of the program, which is not a surprise because I believe the hidden agenda of the policy was to win a landslide election", he said. So it is unlikely anyone tried to stop her leaving, or that they will try to get her back. The island is in the eastern province of Trat, bordering Cambodia.
United Kingdom to pay divorce bill
The paper follows a House of Lords sub-committee report from July on the effect of Brexit on worldwide personal data transfers. Mr Johnson said Britain was a "law abiding" country that would meet its obligations.
There was only "low risk" of unrest following her absence, he added.
What is the trial about?
The rice-pledging programme implemented by the Yingluck government did not only require a colossal budget over three years (late 2011-early 2014), but it also brought about a spate of irregularities and corrupt practices seen in the abuse of public power for personal benefit during the pledging procedures and in fake G2G rice purchase contracts.
Immigration police commissioner Natthathorn Prohsunthorn said he had no information of Ms Yingluck's departure through any legal channel. However, it eventually racked up losses of at least $4.46bn, with Thailand also temporarily losing its leading role as the world's largest rice exporter. This proved highly popular among her supporters in the rural provinces.
May 2011- Yingluck Shinawatra is elected PM, and shortly afterwards begins rolling out her rice subsidy scheme. But Yingluck and her aides have insisted she respects the justice system and would contest her charge to the end.
If Ms Yingluck has joined her billionaire brother Thaksin in self-exile it would be a knock-out blow to the Shinawatra family and their political ambitions. This political connection between Yingluck and her supporters could be put to good use had she been imprisoned.
Ms Yingluck's time in office was overshadowed by controversy as well as strong political opposition.
He remains loathed by the Bangkok royalist elite but cherished by the rural poor. (A thrice-delayed general election is due to be held next year.) The Shinawatra clan has won every election held in the country since 2001 that the military has permitted to take place.
Shinawatra's lawyer, Norawit Lalaeng, said he did not know where she stayed or was being treated, the Bangkoj Post reported. "Now the people have to fight for themselves".
The telecoms tycoon, who once owned Manchester City football club, has not returned since and his Thai passport has been revoked. It is believed he travels between homes in London, Dubai, Hong Kong and Singapore. The scheme was aimed at controlling the rice market to improve prices.