Are any of your other dreams extremely vivid? I've noticed that most people I've talked to have had at least one dream like yours. Maybe it's kinda like a female wet dream thing?! Or maybe it was just that you really miss your SO and your subconscious acted on that in the form of a dream. I know how those are though, I've had plenty of 'em
"You lucky dog" as the saying goes. I don't know why you had such a vivid dream. I've had very few of them myself in my life time. Better stated, "Not enough of them". Most of the time I just dream of dreaming of them, if that makes any sense.
My boyfriend (now my ex) left suddenly about a month ago and I had the same kind of experience a few days ago. I really did feel him there. Unfortunately he wasnt when i work up but i know what you are saying. I think it must be the seperation, makes your body and mind long for what it had.