Apparently the iPhone 4 has already arrived at Walmart. An anonymous tipster sent in a photo to technology website Engadget, showing a picture of the official retail box in storage at Walmart.

The official retail locations in the U.S. where customers will be able to purchase the iPhone 4 on launch day include Walmart, Radio Shack and Best Buy. Unlike the other two retailers, Walmart didn’t take preorders for Apple’s latest iteration of their popular smartphone, instead opting to sell them on a first come, first served basis on the official launch day.

While the official launch date for the new iPhone 4 has been set for June 24, Apple sent out an email on Tuesday suggesting that anyone that pre-ordered the phone directly from Apple might take delivery one day earlier. Recent shipment notifications sent from FedEx seem to provide legitimacy to this possibility.

Walmart, currently the largest chain of retail stores in the United States, carries Apple’s full line of iPods and has been selling their iPhone 3G in most of their stores since 2008.

Walmart hopes to begin selling the iPad before the end of this year, although it is currently only available at Apple’s own retail stores, select Best Buy stores and other assisted locations.