I recently figured something out (Don't know If it already was figured out yet) But it is close to the silence shot with a sniper or typical any gun that 1 shots.
I was playing around in a PVT match and I knived and right after that I used the throwing knife, just like you would do if you are making a silence shot.
What it does, if you got commando pro you can easily LEAP into someone without killing him. It's pretty fun to do so.
If someone have a PVR on PS3 I could demonstrate it and upload it.
It's not that, but it's done the same way. Instead of using it for a shot you use it right after you know, you do the knife leap without actually knifing someone