it was the number 1 rankings in google for many keywords, ranking of 5, suddenly it was de index overnight 3 days ago
Is this site ever been existed really? I see no cached on both Google and Yahoo for this site. If so, this site might have done some critical that caused both Google and Yahoo deindexed on them. The site might have some malware embed in it or similar.
maybe its a new site. I also had the same experience. Went number one on all my articles/posts then all of a sudden, dropped!