There is no legitimate means of removing My Computer that I am aware of so I
suspect it may be a glitch in your registry.  If this problem is less than
five days old, restore a copy of the registry that predates the onset of the
problem and see if that helps.  The five-day limit assumes that the computer
is booted every day.  If it is not booted every day, you may have an old
enough registry backup that you can use even though more than five days have
elapsed.  Any registry changes made after the date of the restored registry
will be lost.

On the Start Menu, select Shut Down and Restart in MSDOS Mode.  At the
Windows prompt, type: scanreg /restore      and hit enter.  Once the
registry restore screen appears, select the date of the registry that you
wish to restore by highlighting it and then click enter.  If you see a
registry named:  Rbbad.cab, that is a copy of the registry that has already
been replaced.

Right-click on the Desktop and select "Line up Icons".

It may just be hiding behind another Icon.

[Any chance of a prankster on the loose here?]

Could it have been accidentally dragged to the recycle bin? Anybody?

It may be as Badour or Candlin have said. Also...

Was it renamed? Click the icon on the top left of the screen. What
opened? You may rename it back by R-Clk the icon, Rename.