One of them appears to have been an accidental loss, not a theft. The other one, at the war memorial, could have gotten washed out of position by rain or ice melt. The third one, however, could potentially be discovered by dozens of students from the nearby school. We cannot foresee all the problems with a cache location. The best we can do is try to place the cache in a reasonable location, and if it doesn't work well, archive it and find another location to place a cache.