With the latest Build 10149 for Windows 10 Mobile, it looks like Microsoft has gotten rid of Lumia Camera, and rebranded it to Windows Camera.
If you search for Lumia Camera in the Store Beta, you would get the Windows Camera instead.
I don't want to jump into conclusions, but I've got to ask is Microsoft getting rid of the Lumia branding?
I guess we will wait and see if more Lumia apps will get rebranded to "Windows".
Maybe the upcoming flagship Windows 10 devices might not be called Lumia also?
We might see Surface Phone and Surface Phone XL...