BW -- That is such a hard place to be, isn't it? So very hard as a parent. Our son came through foster care, also, and we have experienced similar. It hurts. Badly.
What's the longest time he's "disappeared" from contact? Also.... How old is your difficult child?
I think some difficult child's expect us to track them down (wanting it...testing us....do we REALLY love them?). I think other difficult child's couldn't care less and are running amok because it feels good in the moment. Still other difficult child's may "disappear" to conceal things.
We have twice lost contact with our difficult child for 6 months or so. He came back. At the moment things are good with him. But they often have not been in the past, and it's possible they may not be good again in the future. I dunno. I'm content with today. I'll deal with tomorrow when tomorrow comes.
If you don't hear from police or hospitals, he's probably ok. You can always check the local jail roster to see if he's there.
Now, I know this may sound funny, but..... After so many years of this kind of behavior from our difficult child (who's now 24), we eventually opted to "usually" just stop looking. Really. It became required for our sanity and survival. At a certain point, we just said a prayer for him every night and left the rest up to difficult child and God. Have you ever tried that?
We're with you, BW! SEnding prayers of peace your way now...