I had a diff 5 cache that I had searched for several times and couldn't find it (and logged a DNF every time). It was one of those that becomes a mission. I finally called the CO while I was at the cache site, and he offered to come by and make sure it was still there (he hadn't checked on it for a while). Well, he shows up, gets out of the car, and walks directly to the very area I'd searched many times and starts digging with his pocket knife. After a few minutes, he says, "Yep, it's gone." and we start talking geocaching. After a minute, he starts digging again, and uncovers the cache about four inches from where he had dug before. "Oh, here it is" he says as he hands it to me.
Now we could have a whole nother discussion about buried caches. The top of this one had apparently been at ground level when initially hidden, but wind and weather had caused it to sink down and become covered with a layer of dirt, so it was actually buried, even under the "old" rules. My question in this thread is, can I log that as a find? I really didn't want to, because I didn't find it - the CO did, and only after several minutes of searching. The way the cache was buried, I don't think I would have ever found it on my own. In fact, the CO had emailed me previously, telling me exactly what the container looked like and where it was hidden, and I still DNF'd it twice after that. I did, however, sign the log and had the CO's permission to log it as a find, so I did. Of course, after having watched him find it, I could never really "find" it myself.
I suppose that if a group of cachers can go hunting together, and all of them sign the log when one person in the group finds it, this is no different. But I still like to be the one to personally find the container before logging it as a find. Maybe that's why I don't like to cache in a group.