Were the 2nd and 3rd edition PHB's the special re-released editions? Those are relatively new. The ones that were used to raise money for the Gary Gygax fund.
Those were exactly the ones at my local B&N. A couple copies of the 2E and 3.5E re-releases, as well as the Dungeons of Dread and Slave Lord module re-releases. Basically, any of the books that had the brown re-release covers appeared on the shelves alongside a couple remaining 4E books and modules and a couple of the new 5E books.
And let's not forget... thus far there's only been *two* 5E books released thus far. So just how filled can a B&N shelf be with 5E product? Maybe come Christmastime when we have added the MM, DMG and Rise of Tiamat to the first two, we'll have a bit more heft that can fill a more prominent place on the B&N shelves.