1. We have no idea of the geometry of this collision
2. The Syrian MI-17 (regardless of its role) would have been painted in a low-vis camo paint scheme -- the intent of which is to make the aircraft difficult to see against various moving backgrounds.
3. The MI-17 would certainly not have its transponder activated in any mode that would permit (civilian) interrogation and response.
4. Well trained and observant crews in "highly visible" aircraft have had mid-air collisions.
One gets a glimmer of why so many of us who used to be regular contributors to pprune don't post much anymore.
I used to despair. Then I took to simply shaking my head in wonder. Now I just smile.
grizz