When I first began this game, I was afraid to post a DNF, for fear that a cache was actually there, and my inexperience might cause the cache owner to run out and check on it unnecessarily. Frankly, that fear was justified, since after riding with a more experienced cacher one day it became obvious that some of the reported "missing caches" were not really missing. Nowadays, I'm not so reluctant to post the DNF's, because reporting them is important to be sure that caches are properly maintained. Sometimes it also saves me some time when several people have logged consecutive DNF's over a period of time and the CO has logged no response. I generally don't bother looking for those, but send a message to the CO. If there is still no response, I report the cache as needing attention. If the CO does not respond to a volunteer's message within a reasonable time, that cache is usually disabled and ultimately archived. That saves us all the trouble of looking for something that isn't there.
Permission has been granted by the proper authorities for the placement of these caches. Be careful and pull well off the pavement. Watch the terrain rating, by the way; it's a good indication of whether you need to bring boots, and how high the boots have to be! I have left some tradeable goodies and tokens in the container. Be sure and leave yours in the exchange. BYOP.
You are looking for a paint-camoed pill bottle.