The 21-year-old pulled out of the squad for the midweek clash with the Czech Republic in the aftermath of Saturday's draw in Slovakia.
Ireland left the international set-up citing the death of a grandparent, but has since revealed his girlfriend had suffered a miscarriage.
"I wish to explain the circumstances surrounding my departure from the Republic of Ireland international squad," he said in an official Manchester City statement. "When the game ended our manager Stephen Staunton took me outside the dressing room into the corridor, along with the Ireland team doctor. He told me that they had taken a call from my girlfriend, Jessica, and she said my grandmother had died.
"The manager went back into the dressing-room to get my phone and when I got it I immediately rang my girlfriend to get more details.
"My girlfriend was distraught and explained that she had just suffered a miscarriage.
"Jessica said she was very lonely and wanted me to come home. She said she thought they might let me home quicker if they thought my grandmother had died.
"When I finished the call I told the manager and doctor that my grandmother had died and because we were very close I wanted to go home immediately.
"The FAI hired a private jet to get me home and I flew out of Bratislava the following morning. Before I left I told the FAI media officer that the name of my grandmother was Patricia Tallon.
"Early on Monday morning I got a phone call from Stephen Staunton telling me that the FAI had discovered my grandmother in Cork was not dead.
"He wanted to know what was going on and I told him that there had been a mistake and it had been my father's mother. I told him her name was Brenda Kitchener, that she lived in London.
"Jessica and I were still very upset over the miscarriage so we flew home to Ireland for a few days.
"On Thursday, I got a phone call from Manchester City stating that the FAI had discovered that my grandmother, Brenda Kitchener, was also alive.
"I decided at that stage that I must tell truth and admit I had told lies.
"I realise now that it was a massive mistake on my part to tell the FAI and Manchester City that my grandmothers had died and I deeply regret it.
"It was wrong and I sincerely apologise, particularly as I caused a lot of problems for many people."