Listener Question - My Update Disappeared

I saw a notification for an Android update and tapped on it. Then it disappeared and nothing happened?

In most cases updates are handled in the background as they can be large and take time to download. 
You may see a notification (swipe down) showing a download in progress.
Sometimes downloads don’t happen if you’re not on WiFi.
Sometimes updates are paused until after a period of inactivity - maybe overnight.

You should be able to check on the status Settings-> System -> Software Updates
You can also trigger an update from here (if it didn’t start).

Always good to do a phone restart after an update (if it didn’t happen automatically).