I think the Kennet Avenue took another twist and turned towards the farm so the trench missed any stones as they are under the road.
As far as I know there are no free standing stones here but if you did put one on chalk it would leave a large impression in the chalk which could be found.
No on saw a standing stone beyond Beckhampton Cove, the stone Stukeley drew were all flat and could of been dragged away from the Cove.
Of course they could be buried a lot deeper than was thought.
Last nights rain should have cleaned the surface of the trenches up so I'm off out.....