He celebrated his 20th birthday inside the facility, he said.
Since he had stopped smoking synthetic cannabis he could "think straight" and "talk properly" again, he said.
When using K2, all he thought was "when is the next fix" and synthetic cannabis made its users "brain dead", Pine said.
He would be collecting signatures for a petition to have synthetic cannabis banned, he said.
"I am going to help mum."
Mrs Pine said she was happy to have her son out of the "Milton Hilton" and back home.
She had collected 400 signatures for her petition and would be collecting more next Tuesday from 1pm in the Octagon, where she and her son would wear "say no to K2" T-shirts, she said.
The announcement by Associate Health Minister Peter Dunne yesterday on banning two substances included in synthetic cannabis K2 was not enough and it needed to be banned immediately, she said.
"Why can't [Prime Minister] John Key say, as of tomorrow, that's it, no more?"