If you plan to buy AT&T’s first phone with Google’s Android operating system this month, you may be shocked to see that the default Google search engine is missing. Instead, the Motorola device dubbed the “Backflip” will use Yahoo as its default search engine. The phone will hit stores on March 7.

For Google, getting the Android operating system on phones is key to their business model largely because it gets their search engine and mobile ads in front of as many eyeballs as possible. Yahoo, which still runs the second most popular search engine, needs wins like this in the mobile space to increase their market share.

“We have a long-standing relationship with AT&T and more than 80 carrier partnerships around the world for our award- winning mobile-search experience,” David Katz, a vice president at Sunnyvale, California-based Yahoo, said in an e-mailed statement to Business Week. “Mobile search continues to be a focus for investment and innovation.”

Google handles two-thirds of U.S. Internet queries and is the default search engine on the iPhone. Ironically, phone makers who use the Android operating system are not required to set Google search as the default because Android software is open-source. Clearly, Google has a reason to work on developing their own phone hardware to have a say over the default search engine on popular phones.

Mobile phones in the U.S. accessed Google Search more than any other website between January and September 2009 according to data released by The Nielsen Company late last year. Google now accounts for more than 9 percent of all mobile web page views in the U.S., per browser development firm Opera Software’s most recent State of the Mobile Web report–Google’s mobile search portal far outpaces Yahoo (4.3 percent of all page views) and Microsoft’s Bing (just 0.03 percent). Opera adds that search-portal related views make up 13.5 percent of total U.S. mobile page views, with each unique user averaging 39.9 search-based page views per month.