For this test domain I have not been deindexed. I have been sandboxed in the past but have always been able to get un-sandboxed. It's not as hard as most people make it sound. Sandboxing is not a permanent death.
To get out of sandbox I just keep adding content, building new backlinks. Sandbox is also a great to to go page by page and look for ways to improve your SEO. Make sure your meta tags are optimized, your using solid page structure (h1, h2, b, i, etc.). Once you get out of sandbox you will rock. All those links back you up. All of my biggest sites have been through sandbox. When they come out the other end you are golden. I have never had a double dip back into sandbox, so once out I pound the shit out of the site.
I had one site get sandboxed and I doubled downed my effort. Came out the other side with over 500,000 backlinks and page 1 position 1 for hundreds of keywords. Over 25,000 uniques a day. Of course this was back in 2005, but I have done this with smaller websites and even some very recent ones. Just pulled one out of sandbox this week actually and it is making money.
Quick update:
I have added another 17,000 links today. All focused on the main keyword. Position is still #5 page 1 and am receiving steady traffic and might actually pay off the domain today from Adsense. Considering the site is SO young (site was created live only since 4/25), I'd say this one is going pretty damn well.
I have two more sites that are going live this week and I might post on those and some of the things I am doing if people are interested.