Hi Nigel, the Bolt Hole is a house so named, nearby Tuckhill, and as such strictly private. The residents at the time I enquired didn't have any knowledge of the missing stone (or of it's mention), I think (apart from the Stewponey book references) the history of the stone (if it existed) is obscure enough to require some further verification and localising before beginning to wander the fields and hedges, although fields and hedges are always fun to wander :-)
It's tough with just one book to go by. Maybe someone at the local farm (Tuckhill) might have some knowledge passed down?
Let me know please if you turn anything up...
regards,
morfe