Hi Shadow,
A lot of times I don't have a clue.

Usually I don't even know I wasn't here unless I am with T and she sees it or someone says something and I have no clue what they are talking about.
The noise in my head gets much louder though and I have been wondering if that is a sign that I am heading out. Sometimes when T will talk about something (Or something happens outside of T), the noise in my head gets louder and louder and then it stops. Sometimes T will say something like are you back now? Or I'll get a clue that I was gone. I need to talk to T about it, but it seems as if that might be an indicator for me.
Also, sometimes I kind of zip back into the tunnel. I think sometimes I stay there watching maybe and sometimes I check out.
I don't have any control over it right now, but I think with time and work, we can get so we can get grounded instead of skipping out. Recognizing is a first step.