The S4 Sam mobile 5.0 video they released shows the gallery in the app drawer but they don't click on it. Wont be surprised if Gallery is One of those touchwiz preloaded apps, like Google Photos.Was this some odd hybrid build? The reason I ask, you'll notice at about 1:44 he starts playing with Gallery.
Now go look in any of the forums for devices that already have Lollipop - in every single one of them you'll see people saying, "where is the Gallery?!?" - it's been removed, and people are recommending third party software like QuickPic instead.