Chicory,
You did nothing wrong. As everyone else pointed out, he was the one who scared you enough to pick up the phone, and it's his warrants that got him locked up. This was all probably for the best--you get some breathing room, he gets some consequences and, possibly, some help.
Now, my SUGGESTION is that you not bail him out of jail. I've been around the criminal justice system, and my SUGGESTION is that you go to court and/or contact the prosecutor and let them know about his drug problem. The court can make treatment a condition of his probation (assuming his warrants are for things he could get probation for).