when we brought the Fantail aircraft to Paris in 1991, I spoke to the head of EC test, a real professional named Bernard Fouques, about fans. He told me that they had built and flown an experimantal Puma a few years earlier that had a fenestron, and were not particularly happy with the results. he indicated that the slight penalty of a fan on smaller helos became a much greater liability as it scaled up toward the Puma sized aircreaft, so it was dropped.
Perhaps that test aircraft is the one in the sighting?