Were you logged into Google? Did you clear your cache/cookies and change IP before searching the first time? Google personalizes searches, so sites you visit frequently sometime appear much higher than they normally would. Moreover, a searcher's IP address can also have influence over how results are delivered.
My advice is if you have a phone with 3G (iphone, blackberry, et cetera) to type the search on the phone to get a true bearing of where a random visitor might see you in the results.
According to Matt Cutts, Google does not automatically sandbox sites (the sandbox is a myth), because then competitors could build links for their competitors' sites and get them delisted or de-ranked. However, there are filters in place, which can throw a site down if you over-optimize it, which is what some may refer to sandboxing, but these can be easily fixed by changing things around. There are also filters for new domains, which might be your problem.
I don't recommend trying to get past filters (though I know how to, I refuse to try to trick Google). The key to getting top rankings is to deliver great content that people will find useful, don't try to trick the search engines or your potential visitors, and launch that site with a good PR campaign (both print, digital and advertise the hell out of it), and assuming your site is worth the digital ink it's printed on, you'll see yourself in the #1 position in no time assuming you optimize the on-page elements of your site for whatever keyword/category it represents.
