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And though markh never posted again with the results, that was his problem, and his site is now back in the index. His new site was not crawled for about 3 1/2 months after the move.
The good news is that if you do disappear for an index or two then you should hop back afterwards as if nothing happened. (hopefully not two since Google reduce their DNS TTLs a while ago)
It may have helped that both sites were well established with many links to them.
Most browsers and ISP caches will notice the DNS change and visit the new IP after a day or two. Search engines have to visit very many IPs in the crawl (unlike an ISP proxy where people hit the same popular sites often). For this reason, engines tend to cache DNS for longer than other applications. Google seem to be quite quick these days, so hopefully you'll be fortunate.