Lots of those orange markers "disappear" or get moved, but there is nothing grey about true survey data and that is what determines legal boundary. Had a mile of "new" boundary along edge of land here - to my detriment - where neighbor decided to construct a new fence that was at least 20' inside original; he paid for survey and constructed fence accordingly. Funny enough, just bought some trees out in BC and there was hodge-podge of survey ribbons, markers etc from appraisals/sales gone by, but the very old axe blazes that marked the survey reference trees at corners of property were right-on what computer showed when you were standing there. Usually the way people "protect/mark" boundaries gives a pretty good indication of who you are dealing with.
Iíve known farmers who move the survey stake so it corresponds to where they wanted the fence to be! Real stupid idea