I got this message right after I did a non lethal takedown and hid the body in a container. There were no other bodies that I left around and I have not been detected whatsoever. Is this a bug or are the enemies have telepathic implants that make them detect a HIDDEN body from the other side of the building. This had happened more than once on different gigs. At this point I just ignore the stealth system entirely and go crazy guns blazing Rambo on everything.