It's not generally known, but it's true that Stonehenge was repaired in the modern era - I believe it went through some renovation at two different times.
Not that they got it wrong or anything. A stone falls over, even thousands of years after it fell experts can still find exactly where it stood and put it back carefully.
Soil disturbances don't go away and are one of many phenomena used to determine the value of initial investigations like trenches.
Trenching is used all the time when looking for evidence of habitation (for example,) among other things. It's probably the MOST used exploratory tool in the archaeology toolbox. Soil disturbances are what trenching is looking for.
Harte