Try to unplug the mouse and put it back in.

If that does not work then open a terminal and upgrade from there. You may
have a partial upgrade where it upgraded some things and not
others. Sometimes timing plays a role. When you hit the upgrade button it
may not have all of the updates that you need to make it complete.

sudo apt-get update
sudo apt-get upgrade

I would try unplugging once again if it does not show itself. Then I would
try a re-boot. I would also try a different mouse.

I did recover my icon.

I rebooted several times - which didnt help.
With help from another group I did all that you posted here.
Didnt help. Tired a wired and another cordless mouse- nothing.

I was frustrated through the roof after another reboot and when I found my way
with my invisible mouse to start Firefox (because I couldnt get to Chrome), my
icon appeared!

Why in the heck starting firefox would fix my mouse is beyond me but its worked
ever since.

Sometimes we get lucky. I do not understand why some things do not work as
expected and fix themselves mysteriously either, but appreciate it when
they do get fixed. I like to understand things, though, and am frustrated
when I cannot.

Trying to move a mouse around a screen when you dont know where it is to
begin
with... I just had to move very slowly and carefully and look for any sign
that my
cursor moved over something to activate it. But even then, I found it
difficult keep
my mouse in position to click on something. I did manage to accidentally
click on
System and just moving straight down was far more difficult than I thought
it would
be.

if it ever happens again, try using the TAB key on your keyboard. It is
clumsy, but you can still navigate around your desktop and applications using
the keyboard.