The group was discovered in Newhaven, East Sussex, in a refrigerated truck with sparkling water after arriving on a ferry from Dieppe in France.
Seventeen of the group said they were originally 12 to 17 years old and eleven were confirmed at the time as minors when they were found by border guards.
They were placed in the hands of social services, but one has since fled, said a spokesman for the East Sussex County Council.
The children were considered "good" and did not need medical treatment.
In the group, ten adults, five women and five men were interviewed by immigration officers.
An 18-year-old man and a 27-year-old woman have since been removed from the UK. The remaining eight between the ages of 21 and 28 are regularly reported to the Home Office as their cases progress.
Following his arrest, 29-year-old Andrut Mihai Duma was charged with unlawful entry into the UK.
He was remanded to the Lewes Crown Court on November 26.
The case is cited by law enforcement and financial investigations into immigration enforcement.
A spokesman for the East Sussex County Council said: "We can confirm that last Thursday 15 young people were brought into our custody by counterparts of the Border Force and the police found in a lorry in Newhaven.
All were age assessed and found that five are actually adults over 18 years of age.
"The remaining 10 were then either placed with caregivers or assisted housing, depending on their age.
"A young man later fled our custody, which means we still look after nine young people today."
A few months later, another Vietnamese citizen was found in a suitcase hidden behind a trunk in a trunk in Dover Harbor.
The 16-year-old was seriously ill after surviving a 90-minute ferry crossing from Calais and was only discovered when Border Force officers saw an out-of-the-way arm.
20-year-old Romanian citizen Andrei Iancu was sentenced to 18 months in a facility for young offenders following a court case outside Canterbury Crown Court.
In March 2018, Jason Palmer (41) and Richard Giles (39) were arrested at Canterbury Crown Court for supporting illegal immigration to the United Kingdom.
A Vietnamese illegal migrant was found in his vehicle during a Border Force search.
They were sentenced to three years in prison and two years or six months in prison.