Is there a way I can help my boyfriend find his surrendered son?

My boyfriend is a birthdad, in 2007 the girl he had been casually dating told him she was pregnant & disappeared only to show up at his door 4 months later revealing she was also a heroin addict. The baby was born addicted and had to be immediately surrendered. He thinks about his son & says there is no way he can ever track him down because of the way he was taken and I guess the birthmom put on the birth certificate he is addicted to marijuana which is a far cry from her own heroin addiction. Is there a way I can help him find his son or that he could atleast write a letter to the babys parents lawyer or something? I told him he should write a letter, because someday that little boy will grow up and maybe find comfort knowing his dad did love him & thinks about him. I just do not know where to start