The cache IS located at the posted coordinates. You may find the container and sign the log at any time. However, this is a challenge cache, so in order to log a find online, you must meet the qualifications outlined below.
A lot of us look at cache favorite points as we decide which cache to attempt next. When we see a high favorite number beside the cache we read the description and the logs and decide whether its worth going out of our way to log it. It appears that the caches with very high favorite points tend to be rare cache types (virtuals, webcams, GCHQ) in touristy places. So if you go to those places you are likely to qualify for this easily. Otherwise....well maybe you'll need to go to Seattle and visit GCHQ.
This challenge cache requires that the caches you have found have a total of at least 50,000 favorite points. The points per cache are the number of points it has today, not when you logged it. So your point total will increase over time as other people 'favorite' it. You can check your total below. Note that the checker will stop counting points after it hits 50K so it may look like you just made it but you may have a lot more points.
