I sometimes wonder when a site becomes too ruinious to mention - on some maps they show sites which are so ruinious to be barely visible, sometimes they list them so ("rems of"....) and other times they just disappear.
When I visited Glenquickan in 2004, the 1970s map I was using showed a second circle within walking distance, which we tried in vain to find but failed. Then later that day, I looked at the most recent edition of the Landranger map and the circle was no longer marked.