I don't know. Is it classed as child abandonment?
Where has he gone?
It would have been better to contact social services and have them help you. If you really won't have him in the house, they could have found him somewhere to stay.
My god though, to tell your child that you wish you'd never had them
I cannot imagine the state things must be in that those words came out of your mouth, it's hard to imagine ever getting to the point where you could say that to your child. the situation must be horrendous to have seen you get to that point. I'm really sorry. Both for your son to hear those painful words and for you to have got to the point where you snapped and said it. The saddest thing, is that what is said can never be unsaid. It's just so awful for you both, I'm really sorry.
You really need to find out where he is and make sure he has somewhere to be, this may involve an emergency call to social services, telling them you're in crisis.
At the end of the day, he is a fifteen year old child and shutting the door on him is not an option. You have to hand him over to someone.
Horrible as this situation is, it has the potential to be a turning point. with the right intervention, he could use this horrible experience to turn things around.