Apparently it's called the "sandbox" and lots of people run into it. Oh well, just one of those things. Plan of action? Aggressive backlinking as suggested by Jay.

Now I've just got to go find those aggressive backlinks from somewhere.

Totally just made three new buddies today. Sweet.

Aye, it's too early to tell. I had a site that got boosted after the recent Google changes...held its position for about two months, then went totally AWOL.
Yeah, sometimes Google rearranges stuff and sites may disappear or get ranking for a bit and then change back. We'll see. It's just strange that they ALL disappeared over the period of about six hours (last night to this morning).
I guess all I can do is keep working at it. Quitting is for quitters.

How long has the site been up? How are you checking your rankings? how long ago were you indexed?
Google's funny like that. When I find a site of mine has finally been indexed, I also find that it gets a boost in rankings for a bit, and then usually drops. then it recovers over time.

With any luck it's just a reconfiguration of the searches. If you have good content with luck they will come back. Hope it works out for you. I have one that went bye bye and never came back. Others are doing well after disappearing for a few days.