There's something I've wondered about for years, and that is, what happened to the missing stones at Stonehenge? When you look at it, it's obvious that some are missing, and it would be quite a feat to haul one off!
Maybe there just weren't enough stones of a suitable size there in the first place, and so only those were used in its construction. There's enough there to do the astronomical observations and, enough to show exactly where the others should be placed to finish the job.
If memory serves (too busy at the moment to check specific sources) many were indeed hauled off for building stone. The same thing happened at nearby Avebury until the authorities stopped the practice.
The same thing has occurred around the world, including at the Parthenon, the Egyptian pyramids, etc. Humans are notorious and inventive scroungers.