Lee, her son, and I did a virtual cache in Washington DC... There were a few questions to answer in order to log it, we found all but one quickly, and were a couple hours looking everywhere for one answer, and were all ready to DNF it. For some reason I went back to ground zero and looked as if I had never been there - and there it was - right in front of my face.
Trev's "Freedom" Cache (GC39A9) by Trevelyan's R&R and Guy Nelson (3.5/1)
There is also an Earthcache up here that was just DNF'd by someone who was going by the waypoint and thought it was a real cache.
I know someone who DNF'd an event because he showed up a week early and no one was there.
So, it is possible.