Yes, dissociation can be anything from a mild detachment to your surroundings right up to complete loss of reality. There are some disorders where dissociation is more common or to a greater extent, but everyone does it to some degree.

It may well have been you that was distant and not T. Sometimes it can be hard to tell who is the one creating the perceived distance. Part of the whole therapy push/pull thing I guess! It happened to me in my last session, and I'm not sure who it was - maybe it was both of us, we've been going through a rough patch, and she'd been readjusting boundaries - but I think I was subconsciously pulling back in order to protect myself from her 'rejecting' me...

I think it's good you're asking these questions and want to better understand the dynamic between you and T.