A site of mine has completely disappeard from index but is still crawled heavily. Is it banned or just has temporarlily dropped?
Doesn't have to mean that it's banned. Give it some time and see if it comes back up. Meanwhile do some investigating and try to find anything on your site that could be reason for banning it.
I don't like the sound of it, especially if all rankings have gone and not just a few. Keep a close eye on the number of indexed pages with a site: command, and if they start dropping it doesn't look good. I had a site getting xx,xxx uniques a day, and it lost thousands of rankings over night and dropped to 200 uniques a day. That was 3 weeks ago, and it doesn't look like changing. It's been happening to an alarming number of sites lately.
mahmood, The same thing happened to one of my sites a few days ago. I'm still being spidered, the site is PR3 and has no unethical / blackhat content or marketing. My sites less than a year old so I'm assuming it'll sort itself out soon. I share your frustrations though. Good luck.
i do not think it is permanent. Just keep working on your site. I faced this problem earlier but now everything is fine. Just continue with your work...............