A furious Apple has sent tech website Gizmodo a terse letter demanding the return of an iPhone prototype which the site procured. The device was found on a barstool in a pub in Redwood City, California, and was sold by the finder to Gizmodo for a reported sum of $5,000.

As Discoblog reported yesterday, the site immediately declared that the phone was the prototype for the 2010 model of the new iPhone 4G and wrote an in-depth article detailing all its new features. The article, accompanied by photos and video, drew an estimated 3 million viewers to the Web page in just 12 hours online. Some of those viewers must have been Apple’s lawyers.

In the letter dated yesterday, Apple’s senior counsel wrote: “It has come to our attention that Gizmodo is in possession of a device that belongs to Apple. This letter constitutes a formal request that you return the device to Apple. Please let me know where to pick up the unit.”

The phone, Gizmodo revealed, was found in a bar, camouflaged to look like a regular iPhone 3GS. But when the finder switched on the device, he found that the mobile Facebook app was logged in to the account of Gray Powell, an Apple software engineer whose last post on the social networking site was reportedly “I underestimated how good German beer is” [ABC News]. The guy who found the phone reportedly tried to get in touch with the person who lost it, to no avail. That is when the finder is reported to have started shopping the phone around; selling pictures of the phone first to Engadget and then selling the device to rival Gizmodo for $5,000.

Gizmodo’s subsequent blog post on the phone drew massive traffic, with paidcontent.org estimating that just one post generated more than 3.7 million page views, over 28,000 tweets and more than 1,870 comments [Fortune]. That’s when Apple swung into action, getting in touch with the site and asking for it to cough up the prototype. Gizmodo says it has since returned the phone to Apple on the condition that the company “take it easy on the kid who lost it.” Gizmodo’s editorial director Brian Lam added, “I don’t think he loves anything more than Apple.”

For a sneak peak at the new features of Apple’s next generation iPhone, go to Discoblog’s post: So, a Guy Walks Into a Bar… and Discovers Apple’s Latest iPhone.

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Image: Gizmodo