This rang a big bell with me: "may never have been "fixed" to the surface in a way that would leave an archaeological record".... So what are we to make of Stukeley, called a liar for centuries for drawing the Beckhampton Ave so long, proved not a liar over six stones, but no record yet found of the others. Was he drawing relatively small stones placed on the surface that left no marks when removed?
Stukeley's work is so tantalising because he was there in relatively modern times, and much of what he definitely did see isn't there any longer. But the problem comes that it's sometimes difficult to separate those times when he was drawing what he saw (but we can't see because it's gone since his time) and those times when he was drawing his own speculative reconstructions.