Plugin Update Verification: Check for Plugin Existence

"Moving onto something else within the dashboard site: updates. After plugin updates the dashboard should confirm that the status of each updated plugin has not changed, even check that the plugin still exists in each site it was previously in? Sometimes plugins get deleted on update (this is a known WP issue that affects mostly multisites but which can affect regular sites too). So, has the updated plugin deactivated itself? Is it still active? Has it vanished? These are important questions to answer for every site admin after plugin updates."

~ Split by Dennis from a larger post by Lee.