Sure it does exist. But as I see it, it runs at 3.06GHz. http://ark.intel.com/Product.aspx?id=39312
The T9900 are for mobile. I believe they are completely different family with the i7 which incidentally also have mobile versions.
This makes everything absolutely clear. No, the chip you've listed does not exist. You are correct in your assertion that the T9900 and i7 chips are different. People that list things on ebay often don't know anything about the product they're selling.