I wish I had some good ideas, but I know you can get good support here. You can post as much as you want, and there will always be someone who cares.
I just hope your son will get help, on his own, and that you will protect your things in the mean time. I have heard of so many addicts stealing from their own family. Just don't be unaware of the lengths they will go to. If he had a needle and an empty bag on him, surely he must have used very recently, and will be having withdrawals.
He will probably expect you to help him, with more pills, maybe. As Ann said, don't let yourself be tempted to get him drugs, illegally. why make it easier for him, when he really needs to go for rehab?
best wishes for you and your son. We are here for you.
chicory