I experienced a very similar state not to long ago. It was essentially what you described. Feelings of being almost distanced from the body, a dullness of physical sensation ect. The main thing I noticed about this state of concentration was that when I would exit meditation, it was like waking up. I wasn't exactly sure of exactly what was accomplished, the meditation was hazy like a dream. I decided this was what Ajahn Fuang called "moha-samadhi", or "delusion-concentration." Thanisarro Bhikkhu speaks of it in a few dhamma talks, but the only one I could find quickly didn't have a very long explanation.
"Jhana Not by the Numbers"
http://www.accesstoinsight.org/lib/auth ... mbers.html
...The best state of concentration for the sake of developing all-around insight is one that encompasses a whole-body awareness. There were two exceptions to Ajaan Fuang's usual practice of not identifying the state you had attained in your practice, and both involved states of wrong concentration. The first was the state that comes when the breath gets so comfortable that your focus drifts from the breath to the sense of comfort itself, your mindfulness begins to blur, and your sense of the body and your surroundings gets lost in a pleasant haze. When you emerge, you find it hard to identify where exactly you were focused. Ajaan Fuang called this moha-samadhi, or delusion-concentration.
The second state was one I happened to hit one night when my concentration was extremely one-pointed, and so refined that it refused settle on or label even the most fleeting mental objects. I dropped into a state in which I lost all sense of the body, of any internal/external sounds, or of any thoughts or perceptions at all — although there was just enough tiny awareness to let me know, when I emerged, that I hadn't been asleep. I found that I could stay there for many hours, and yet time would pass very quickly. Two hours would seem like two minutes. I could also "program" myself to come out at a particular time.
After hitting this state several nights in a row, I told Ajaan Fuang about it, and his first question was, "Do you like it?" My answer was "No," because I felt a little groggy the first time I came out. "Good," he said. "As long as you don't like it, you're safe. Some people really like it and think it's nibbana or cessation. Actually, it's the state of non-perception (asaññi-bhava). It's not even right concentration, because there's no way you can investigate anything in there to gain any sort of discernment. But it does have other uses." He then told me of the time he had undergone kidney surgery and, not trusting the anesthesiologist, had put himself in that state for the duration of the operation.
In both these states of wrong concentration, the limited range of awareness was what made them wrong. If whole areas of your awareness are blocked off, how can you gain all-around insight? And as I've noticed in years since, people adept at blotting out large areas of awareness through powerful one-pointedness also tend to be psychologically adept at dissociation and denial. This is why Ajaan Fuang, following Ajaan Lee, taught a form of breath meditation that aimed at an all-around awareness of the breath energy throughout the body, playing with it to gain a sense of ease, and then calming it so that it wouldn't interfere with a clear vision of the subtle movements of the mind. This all-around awareness helped to eliminate the blind spots where ignorance likes to lurk...
I hope this helps.