There are two possibilities:
1. They no longer running PPC campaigns at the time when we crawled the data
2. They are still running PPC campaign, but their ads are no longer in the top 10 rank.
3. They're running a geo targeted PPC campaign which we are unable to track.
iSpionage tend to give you the best data of your competitors PPC strategy, so that you will have an accurate data to spy or learn from them. That's why we give you only the top ten PPC advertisers. If the URL you're looking for is not on the top ten list when we crawl our engine, then we may not show their result