For those awaiting an iPhone 4 nervously watching the rumor mills, it’s nice to know that we now have confirmation of iPhones showing up at multiple retail outlets.

We ran a story the other day reporting repackaged iPhone 3GS units arriving in stores in preparation for sale on Thursday. Now, Engadget is reporting iPhone 4 units being sighted at both Wal-Mart and Best Buy retail stores:

Unfortunately, like every other previous iPhone launch, there is no information on quantity of units at each location. We also have no sightings of the mysterious white iPhones that are not yet available for preorder or reservation through any retailer.

With worries about shortages running high, it should settle some nerves to see that units are on hand in store, at least at these two chains.