Are you sure your not using Google SearchWiki and you've bumped it up yourself? Only joking.... I'm glad SEO isn't that easy or i'd be out of a job!
Google Dance Had similar affect before was scoring number one all of a sudden dropped to the 2nd page bottom. Had to work on it again and bring it back to the first page but still not on top yet
Two possibilities... One, Google just did update. So it can be a temporary bug. Two, it does that sometimes. I also had a web hosting site and the only thing I did was purchase the keyword domain and it just did a trick. I was in No.1 position for the very competitive keyword and it remains in that position even till now. (this is in Google) So hopefully your site might stay in that position if it happened due to the 2nd possibility. Regards, Joseph
If you are using the domain name as the keywords when searching, then Google will probably fetch your site first.