I have a new website that's about 1-2 months old. I've gotten some good backlinks lately and it finally hit first page of a 1.5million results keyword. It was actually number 5. I was hovering on the second page for quite a while too. The day AFTER I hit number 5 (Today) I can't find my site for that keyword at all! I went all the way to page 10! I was ranking for a few other keywords and I checked them and I was gone too... The only thing I'm ranking for right now is my website name =/ Is this the sandbox? Will this only be temporary? Someone help please
I have not been keeping up to date with sandbox developments lately but what you describe was symptomatic of being in the sandbox as I remember it. A few weeks after a site is submitted it often spring from nowhere to near the top of the results before disappearing again. You'll probably have to wait a bit longer.