That would make it sound like it's either an .htaccess file or some other redirect code.
How did you look for the .htaccess file? Some FTP clients might need a preference set to view hidden files.
Does it only happen with the index file? Try accessing something else, like an image, to see if that redirects.
If everything redirects, I'm guessing .htaccess. If you can't figure out your FTP program's settings, you should be able to see an .htaccess file with webftp.dreamhost.com
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