My mistake – should have done more research! Big Sweetie and I visited again today, in the company of 2 other Scottish Megaraks. The stump of one of the other stones in the group is visible 5m east of the survivor. Hidden down in the turf again about 5m south lies a recumbent pillar which was probably part of the group. I have uploaded 3 photos, 2 showing the relationship of the survivor and stump, and one showing the recumbent with turf peeled back (thanks, Milgi!).