How/Where does Lightroom Classic desktop store photos added to its library on Lightroom mobile?

Suddenly noticing missing images in my Lightroom Classic desktop library.  Exclusively images that have been added to my Lightroom Mobile library from my phone's camera roll.  I've recently adjusted my backup workflow so I'm sure it's something I've done wrong.  Just trying to find out how Lightroom is designed to handle/store these files normally so I can see how I've messed it up and correct the problem.  I'm signed in to my (only) Adobe account on all macines/devices.  I'm up to date on all software, OS/iOS, etc.  Macbook Pro 16 in 2019.  Didn't post as a "Bug" since I'm fairly certain it's not a program issue but rather something I've fumbled in my backup switch.