I had the thing you are talking about happen to me, too. My site was alright, and then it was deindexed. I didn't do any linkbuilding to it ever, really. I thought possibly it's because I didn't post any content on it for weeks, but that shouldn't result in deindexed.
I will think about moving it to another server.
Does "Unnatural inbound links" deindex site? I thought it only affects your ranking? So far there is no official way to recover from Google Deindexation hammer.
I have seen a few cases like this on blogs and forum. You can try googling.
So far, it only works for inbound links penalty. (not for manual spam, outbound etc)
Wish it works for deindexed domains![]()