His father has left him - from Anonymous

Hello. Please can you not print my name and details. Thank you.
My son is having a hard time. He is 17 and when he was 14 I asked his dad to leave our family home because he was using drugs. His dad had been clean for roughly 7 years but looking back I am not 100% he was. Anyway, 3 years ago I finished our relationship because I found a needle hidden in our bathroom.
I haven't been in touch with my ex since and he hasn't been in touch with our son which is heartbreaking because he and our son were very close. 
I find it sickening that drug addicts can turn their backs on the people closest to them but then why should any child be subjected to a drug addict parent who lives a life full of pipe dreams and false promises? I have flourished and feel good about myself and the best thing I did was to get rid of my ex. But my son has very much been affected by the break up and the fact his dad hasn't bothered to even phone him. He knows his dad is a heroin addict and I often find my son googling about heroin and how this evil drug changes people, not for the better might I add, but for the worse. How do I help him to come to terms with this? Thanks, Anonymous. 

COMMENT: One of the best community forums we can recommend is:         Sober Recovey.  They host forums for families and the threads are extremely supportive ones.