The app was installed on a phone belonging to a heavily pregnant woman and was taken during a robbery.
Christopher Robinson (18), of Clanranald Road, Donnycarney, Dublin was found guilty of robbery of an iPhone from the woman on the evening of January 21.
He was a juvenile at the time, but has since reached adulthood and had been released on a suspended sentence two months before the mugging.
Dublin Children's Court heard that the woman, who was 27 weeks' pregnant, had been talking to her husband on the phone walking near her home, at Collins Park, in Donnycarney when she was approached from behind by two people.
She was knocked to the ground and suffered bruising to her face and grazing on her hands as she tried to protect her unborn child.
She identified the teenager for Garda James Nugent at a chip shop in Marino about 40 minutes later after her husband traced the phone by using the Find My Friends app.
Gda Nugent said that the teenager admitted being present but denied being involved in the robbery.
Judge O'Connor said he was satisfied beyond reasonable doubt that the youth was guilty of the robbery charge.
He is to be sentenced later in the Children's Court.