when the home page no found in google search?it means google rank was down?
There are different possible reasons why your homepage is not yet found in Google Search.
How old your site it? Much better if you will have a page keyword targeting. Focus on it.
If your homepage is not listed in Google you will have no rank whatsoever, it's pretty simple.
Have you submitted your site to Google for indexing yet?
If so, how long ago?
It can take a month or so sometimes.