I wish to SINCERELY THANK YOU - - each one who responded!  You were right - - I simply reinstalled it and it is back to normal.  I have been using computers since 1990, and this was the first time I had ever seen an app I had installed DISAPPEAR completely from the computer.  The only thing I've done differently now is clicked "Keep in dock".  Maybe that is what I neglected to do last time.  Once again, THANK YOU generously to everyone who responded.  Much appreciated.

I was using a software wallet from Electrum.org, which displayed a beautiful atomic symbol on the dock at the bottom of my Mac screen.  When clicking on the symbol icon, it would display the window showing balances, history, etc.  Then upon restarting the computer, it disappeared!  It is not on the dock.  It is not in Launcher.  It is not in Applications.  I found the electrum folder in Finder, but that only consists of a lot of documentation - - no app, no wallet.  Where is it?  How to restore it?  And how to prevent it from disappearing again?

I was using a software wallet from Electrum.org, which displayed a beautiful atomic symbol on the dock at the bottom of my Mac screen.  When clicking on the symbol icon, it would display the window showing balances, history, etc.  Then upon restarting the computer, it disappeared!  It is not on the dock.  It is not in Launcher.  It is not in Applications.  I found the electrum folder in Finder, but that only consists of a lot of documentation - - no app, no wallet.  Where is it?  How to restore it?  And how to prevent it from disappearing again?