*cringe*
I was that daughter. As a teen and very young adult, when my emotions, especially anger at being neglected (that was my specific situation) were more than I could cope with, I would bail out for awhile, often not telling anyone where I was going. And I would say: "There are two possibilities: I'm okay or I'm not, and either way, there isn't much you can do about it." (I'm more considerate now, and I do check in calls if I'm going to be on the road, but I still think I had a point about that.)
The more bent out of shape my family got about it, the more I asserted my independence in the most obnoxious way possible just to prove that 1. I could do what I wanted and 2. I existed and was a person to be reckoned with. When they ignored my bad behavior and interacted with me in a positive way, I acted in a more mature manner.
As for it being difficult to detach: personally, the more I harbor the illusion that I can control something, the harder it is to detach. When I'm fully aware that there's nothing I can do, detaching gets to be automatic. (Of course, my kid is 11, and if she disappeared I'd hit the roof for reasons having to do with her being a child. We'll see how I do when she's 17 and spreading her wings.)