My son did the exact same thing. After three months in rehab, he called me and said he couldn't handle it anymore and asked to come and get him. I told him to stay and finish the program and that I would not come and get him. So he called someone else to come and get him and they did.
Shortly after that he hit the streets searching for money and drugs...ended up in jail for theft. Judge sentenced him to court ordered rehab for six months (that he cannot leave) and then four years probation.