The 51-year-old millionaire walked free from Wheatfield prison under the cover of darkness at 12.15am yesterday.
The wealthy businessman -- who rugby tackled his victim to the ground before sexually assaulting her -- sped off in a waiting BMW and has not been seen since.
There was no sign of him at his home on Griffith Avenue, Dublin, yesterday.
A neighbour who is close to the victim's family told the Herald they were not surprised that Lyons had chosen to avoid the spotlight.
"He hasn't been seen since his release and the family believe he has 'gone to ground.' The way he left the prison after being released in the middle of the night shows he's a coward," he said.
"It's noteworthy that a man who attacked a woman in the middle of the night is released on to the streets by the Government in the middle of the night."
Lyons served just four and a half months in prison after Judge Desmond Hogan suspended five and a half years of a six-year sentence.
He ordered the father of four to pay €75,000 to his victim.
Although the judge said the attack involved "violence of a seriously frightening nature," he took into account his "good character" and the unlikeliness to reoffend.
The victim's family were incensed at the outcome and the Director of Public Prosecution appealed against the leniency of the sentence.
The friend said the family was taking a close interest in the progress of the appeal, which is listed for mention in the Court of Criminal Appeal on Monday when a date may be set for a hearing.
Lyons, a high-profile aviation broker, claimed in court his cholesterol medication, cough syrup, and alcohol made him assault the 27-year-old woman in October 2010.