i just had a dream where i was flying and i flew straight up in the air and landed in some gray place that i couldnt get out of… i could feel the floor under my feet but could not see anything but gray. i had to wake up to get free of where i was… it wasnt a LD. 
maybe instead of a black void it was a gray void. Happens when you enter NREM
Sounds like it was just a normal dream. Nothing in particular to worry about. If you were lucid you would have known you could get out of the “gray void “ when ever you want.
Good luck
Perhaps he means that he flew into the gray void, still knew he was dreaming, but couldn’t do anything to affect the suroundings? Maybe it was your sub-C trying to keep you in line. In fact either way I’d say it was your sub-C.
Maybe you flew in to a buffersone, between dream and a astral plane/OOBE experience. ^-^