I found the problem !
(Well, maybe I didn't so much
find the problem, but I fixed it so the printer
doesn't uninstall itself any more)
Back on Feb. 9, I made this post:
I also have a Samsung printer/scanner/copier that is connected via ethernet cable to my home network.
I could not get the scanner to work no matter what I tried.
After much researching, I finally found a solution.
On the printer menu, I gave the printer a static address,
in my case it is 192.168.2.111.
Then I added the line, tcp 192.168.2.111
to /etc/sane.d/xerox_mfp.conf
Like magic, the scanner then worked."Well, I think that after a recent update (maybe), the printer
was uninstalled and then the next time I booted the computer
with the printer on, the computer assigned a 'device URI' of it's own choosing.
Anyway, after this last time of starting the computer with the
printer on, I finally noticed that the 'device URI' was not what
I originally assigned so that the scanner would work, namely
http://198.168.2.111.
So, I changed the 'device URI' back to
http://198.168.2.111and made a test by turning off the printer, turning off the computer,
and then booting up the computer with the printer off.
Now, the printer does not uninstall itself and when I power up
the printer, everything works like it should.
Hopefully, this might help someone in the future that has
a similar problem.