Welcome to SR!
I agree with the above...focus on yourself.
I'm a recovering crack addict, and the first sign that I was using was when no one could get hold of me. It will do no good to try to track him down, or worry about him. He's doing what he wants to do and you can't change that.
Three c's...you didn't cause it, can't control it, and you can't cure it.
Most addicts eventually come back around, and have some story of why they "disappeared". Go with your gut. Decide if this is what you want in a relationship. Read around some other threads and see what others have gone through, being in relationships with A's (addicts). It's not pretty.
If he has access to any joint accounts, I would seriously consider changing that to limit or stop his access. He could drain out a bank account rather quickly.
Keep coming back here. There are a lot of wonderful people here, with a ton of ES&H (experience, strength and hope). You're not alone.
Hugs and prayers!
Amy